A nitride semiconductor light-emitting element includes: a substrate; a rectangular semiconductor stack structure including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer stacked in sequence above a main surface of the substrate; a p-side contact electrode in contact with the p-type semiconductor layer in a p-side contact region; and an n-side contact electrode in contact with the n-type semiconductor layer in an n-side contact region. In a plan view of the main surface, the semiconductor stack structure includes a first corner portion, the n-side contact region includes a linear first region extending in one direction from a first starting point spaced apart from the first corner portion, the p-side contact region is disposed between the first starting point and the first corner portion where the distance therebetween is less than or equal to 0.26 times the length of a shorter side of the semiconductor stack structure.

FIELD

The present disclosure relates to a nitride semiconductor light-emitting element.

BACKGROUND

Nitride semiconductor light-emitting elements are used as a light source of automotive headlamps, etc. Automotive headlamps are increasingly miniaturized and becoming high-power. Accordingly, nitride semiconductor light-emitting elements used for automotive headlamps are also desired to be miniaturized and become high-power.

For example, in the nitride semiconductor light-emitting element described in Patent Literature (PTL) 1, current is injected into a wide range of an n-type semiconductor layer by causing an n-side electrode in contact with the n-type semiconductor layer to have an annular shape. This is an attempt to improve the luminance of the nitride semiconductor light-emitting elements.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

However, the conventional nitride semiconductor light-emitting elements described in PTL 1, etc., fail to sufficiently reduce the loss component of the forward voltage that does not contribute to light emission. For this reason, the utilization efficiency of power has not been sufficiently improved in the conventional nitride semiconductor light-emitting elements. In addition, when the loss component of the forward voltage increases, the amount of heat generated in the nitride semiconductor light-emitting element increases, leading to a decrease in the performance and reliability of the nitride semiconductor light-emitting elements.

The present disclosure solves such problems and provides a nitride semiconductor light-emitting element that is capable of reducing the forward voltage.

Solution to Problem

In order to solve the above-described problems, a nitride semiconductor light-emitting element according to one aspect of the present disclosure includes: a substrate; a semiconductor stack structure including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer stacked in sequence above a main surface of the substrate, the semiconductor stack structure having a rectangular shape in a plan view of the main surface; a p-side contact electrode disposed above and in contact with the p-type semiconductor layer in a p-side contact region; and an n-side contact electrode disposed above and in contact with the n-type semiconductor layer in an n-side contact region. In the nitride semiconductor light-emitting element, in the plan view of the main surface, the semiconductor stack structure includes a first corner portion, the n-side contact region includes a first region having a linear shape and extending in one direction from a first starting point that is spaced apart from the first corner portion, the p-side contact region is disposed between the first starting point and the first corner portion, and distance r1that is a distance between the first corner portion and the first starting point is less than or equal to 0.26 times length a of a shorter side of the semiconductor stack structure.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the semiconductor stack structure includes a second corner portion disposed on a same side of a rectangular outer edge of the semiconductor stack structure as the first corner portion, the n-side contact region includes a second region having a linear shape and extending in one direction from a second starting point that is spaced apart from the second corner portion, the p-side contact region is disposed between the second starting point and the second corner portion, and distance r2that is a distance between the second corner portion and the second starting point is less than or equal to 0.26 times length a of a shorter side of the semiconductor stack structure.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the second region may intersect.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, an extended line of the first region and an extended line of the second may intersect.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the semiconductor stack structure may include a third corner portion disposed diagonally to the first corner portion and a fourth corner portion disposed diagonally to the second corner portion, the n-side contact region may include a third region having a linear shape and extending in one direction from a third starting point that is spaced apart from the third corner portion, and a fourth region having a linear shape and extending in one direction from a fourth starting point that is spaced apart from the fourth corner portion, the p-side contact region may be disposed between the third starting point and the third corner portion, and between the fourth starting point and the fourth corner portion, and distance r3that is a distance between the third corner portion and the third starting point may be less than or equal to 0.26 times length a of the shorter side, and distance r4that is a distance between the fourth corner portion and the fourth starting point may be less than or equal to 0.26 times length a of the shorter side.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the third region may be connected to each other, the third region being disposed on an extended line of the first region, the second region and the fourth region may be connected to each other, the fourth region being disposed on an extended line of the second region.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the third region may extend in the same direction, and the second region and the fourth region may extend in the same direction.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the third region may be disposed on an extended line of the first region and spaced apart from the first region, the fourth region may be disposed on an extended line of the second region and spaced apart from the second region.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the third region may extend in the same direction, and the second region and the fourth region may extend in the same direction.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the n-side contact region may include: a fifth region disposed between the first region and the third region and spaced apart from each of the first region and the third region, the fifth region having a linear shape; and a sixth region disposed between the second region and the fourth region and spaced apart from each of the second region and the fourth region, the sixth region having a linear shape, and the fifth region and the sixth region may intersect.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region, the second region, the third region, and the fourth region may be spaced apart from one another.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, proportion b of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface may be less than or equal to 0.3.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, r1=r2=r3=r4, and 0<r1/a<−0.54b2+0.59b+0.16 may be satisfied where: r1denotes the first distance that is the distance between the first corner portion and the first starting point, r2denotes the second distance that is the distance between the second corner portion and the second starting point, r3denotes the third distance that is the distance between the third corner portion and the third starting point, r4denotes the fourth distance that is the distance between the fourth corner portion and the fourth starting point; a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d1=d2=d3=d4, and0<d1/a<1.41b2−1.13b+0.55 may be satisfied, where: d1denotes a distance between the first region and the fifth region; d2denotes a distance between the second region and the sixth region; d3denotes a distance between the third region and the fifth region; d4denotes a distance between the fourth region and the sixth region, a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d1=d2=d3=d4, and0<d1/a<−0.92b2+1.12b+0.05 may be satisfied, where: d1denotes a distance between the first region and the fifth region; d2denotes a distance between the second region and the sixth region; d3denotes a distance between the third region and the fifth region; d4denotes a distance between the fourth region and the sixth region, a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d5=d6, and0<d5/a<1.06b2−0.95b+0.61 may be satisfied, where: d5denotes a fifth distance that is half a distance between the first region and the third region; d6denotes a sixth distance that is half a distance between the second region and the fourth region; a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d5=d6, and0<d5/a<−0.95b2+0.89b+0.11 may be satisfied, where: d5denotes a fifth distance that is half a distance between the first region and the third region; d6denotes a sixth distance that is half a distance between the second region and the fourth region; a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the second region may be connected to each other.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the n-side contact region may include: a first additional region having a linear shape and extending from the first starting point in a direction different from a direction of the first region; a second additional region having a linear shape and extending from the second starting point in a direction different from a direction of the second region; a third additional region having a linear shape and extending from the third starting point in a direction different from a direction of the third region; and a fourth additional region having a linear shape and extending from the fourth starting point in a direction different from a direction of the fourth region, the first region and the second additional region may be connected to each other, the second region and the third additional region may be connected to each other, the third region and the fourth additional region may be connected to each other, and the fourth region and the first additional region may be connected to each other.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first region and the second additional region may extend in the same direction, the second region and the third additional region the third region and the fourth additional region may extend linearly in the same direction, and the fourth region and the first additional region may extend in the same direction.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the second region may be disposed on an extended line of the first region and spaced apart from the first region. The second region may extend in a same direction as the first region

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the n-side contact region may include: a first additional region having a linear shape and extending from the first starting point in a direction different from a direction of the first region; a second additional region having a linear shape and extending from the second starting point in a direction different from a direction of the second region; a third additional region having a linear shape and extending from the third starting point in a direction different from a direction of the third region; and a fourth additional region having a linear shape and extending from the fourth starting point in a direction different from a direction of the fourth region, the second additional region may be disposed on an extended line of the first region and spaced apart from the first region, the second additional region extending in the same direction as the first region, the third additional region may be disposed on an extended line of the second region and spaced apart from the second region, the third additional region extending in the same direction as the second region, the fourth additional region may be disposed on an extended line of the third region and spaced apart from the third region, the fourth additional region extending in the same direction as the third region, and the first additional region may be disposed on an extended line of the fourth region and spaced apart from the fourth region, the first additional region extending in the same direction as the fourth region.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, r1=r2=r3=r4, and0<r1/a≤0.26 may be satisfied where: r1denotes the first distance that is the distance between the first corner portion and the first starting point, r2denotes the second distance that is the distance between the second corner portion and the second starting point, r3denotes the third distance that is the distance between the third corner portion and the third starting point, r4denotes the fourth distance that is the distance between the fourth corner portion and the fourth starting point; a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, r1=r2=r3=r4, and −0.26b+0.15<r1/a≤0.26 may be satisfied where: r1denotes the first distance that is the distance between the first corner portion and the first starting point, r2denotes the second distance that is the distance between the second corner portion and the second starting point, r3denotes the third distance that is the distance between the third corner portion and the third starting point, r4denotes the fourth distance that is the distance between the fourth corner portion and the fourth starting point; a denotes the length of the shorter side; and b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d7=d8=d9=d10, and −2.50b2+1.75b−0.15<d7/a<−0.30b+0.35 may be satisfied where: d7denotes a seventh distance that is a distance between the first region and the second additional region, d8denotes an eighth distance that is a distance between the second region and the third additional region, d9denotes a ninth distance that is a distance between the third region and the fourth additional region, d10denotes a tenth distance that is a distance between the fourth region and the first additional region; a denotes the length of the shorter side; and b denotes a proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, b≤0.3, d7=d8=d9=d10, and0<d7/a<−5.20b2+2.09b+0.09 may be satisfied where: d7denotes a seventh distance that is a distance between the first region and the second additional region, d8denotes an eighth distance that is a distance between the second region and the third additional region, d9denotes a ninth distance that is a distance between the third region and the fourth additional region, d10denotes a tenth distance that is a distance between the fourth region and the first additional region; a denotes the length of the shorter side; and b denotes a proportion of an area of the n-side contact region to an area of the semiconductor stack structure in the plan view of the main surface.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, the nitride semiconductor light-emitting element may include: a substrate; a semiconductor stack structure including an n-type semiconductor layer, an active layer, and a p-type semiconductor layer stacked in sequence above a main surface of the substrate, the semiconductor stack structure having a rectangular shape in a plan view of the main surface of the substrate; a p-side contact electrode disposed above and in contact with the p-type semiconductor layer in a p-side contact region; and a plurality of n-side contact electrodes disposed above the n-type semiconductor layer, each of the plurality of n-side contact electrodes being in contact with the n-type semiconductor layer in a corresponding one of a plurality of n-side contact regions arranged in a matrix of at least three rows and three columns. In the nitride semiconductor light-emitting element, in the plan view of the main surface, the semiconductor stack structure may include a first corner portion, the plurality of n-side contact regions may include: a first n-side contact region disposed in closest proximity to the first corner portion; a first Xn-side contact region disposed adjacent to the first n-side contact region in a row direction; and a first Yn-side contact region disposed adjacent to the first n-side contact region in a column direction, the first n-side contact region may be disposed in a first unit having a rectangular shape, the first unit being enclosed by: a straight line that is equidistant from a center of gravity of the first n-side contact region and a center of gravity of the first Xn-side contact region; a straight line that is equidistant from the center of gravity of the first n-side contact region and a center of gravity of the first Yn-side contact region; and an outer edge of the semiconductor stack structure, the first n-side contact region may include a first region having a linear shape and extending in one direction from a first starting point that is spaced apart from the first corner portion, the p-side contact region may be disposed between the first starting point and the first corner portion, and distance r1that is a distance between the first corner portion and the first starting point may be less than or equal to 0.26 times length a1 of a shorter side of the first unit.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the semiconductor stack structure may include a second corner portion disposed on a same side of a rectangular outer edge of the semiconductor stack structure as the first corner portion, a third corner portion disposed diagonally to the first corner portion, and a fourth corner portion disposed diagonally to the second corner portion, the plurality of n-side contact regions may include: a second n-side contact region disposed in closest proximity to the second corner portion; a second Xn-side contact region disposed adjacent to the second n-side contact region in a row direction; a second Yn-side contact region disposed adjacent to the second n-side contact region in a column direction; a third n-side contact region disposed in closest proximity to the third corner portion; a third Xn-side contact region disposed adjacent to the third n-side contact region in a row direction; a third Yn-side contact region disposed adjacent to the third n-side contact region in a column direction; a fourth n-side contact region disposed in closest proximity to the fourth corner portion; a fourth Xn-side contact region disposed adjacent to the fourth n-side contact region in a row direction; and a fourth Yn-side contact region disposed adjacent to the fourth n-side contact region in a column direction, the second n-side contact region may be disposed in a second unit having a rectangular shape, the second unit being enclosed by: a straight line that is equidistant from a center of gravity of the second n-side contact region and a center of gravity of the second Xn-side contact region; a straight line that is equidistant from the center of gravity of the second n-side contact region and a center of gravity of the second Yn-side contact region; and an outer edge of the semiconductor stack structure, the third n-side contact region may be disposed in a third unit having a rectangular shape, the third unit being enclosed by: a straight line that is equidistant from a center of gravity of the third n-side contact region and a center of gravity of the third Xn-side contact region; a straight line that is equidistant from the center of gravity of the third n-side contact region and a center of gravity of the third Yn-side contact region; and an outer edge of the semiconductor stack structure, the fourth n-side contact region may be disposed in a fourth unit having a rectangular shape, the fourth unit being enclosed by: a straight line that is equidistant from a center of gravity of the fourth n-side contact region and a center of gravity of the fourth Xn-side contact region; a straight line that is equidistant from the center of gravity of the fourth n-side contact region and a center of gravity of the fourth Yn-side contact region; and an outer edge of the semiconductor stack structure, the second n-side contact region may include a second region having a linear shape and extending in one direction from a second starting point that is spaced apart from the second corner portion, the third n-side contact region may include a third region having a linear shape and extending in one direction from a third starting point that is spaced apart from the third corner portion, the fourth n-side contact region may include a fourth region having a linear shape and extending in one direction from a fourth starting point that is spaced apart from the fourth corner portion, the p-side contact region may be disposed between the second starting point and the second corner portion, between the third starting point and the third corner portion, and between the fourth starting point and the fourth corner portion, and distance r2that is a distance between the second corner portion and the second starting point may be less than or equal to 0.26 times length a2 of a shorter side of the second unit, distance r3that is a distance between the third corner portion and the third starting point may be less than or equal to 0.26 times length a3 of a shorter side of the third unit, and distance r4that is a distance between the fourth corner portion and the fourth starting point may be less than or equal to 0.26 times length a4 of a shorter side of the fourth unit.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the plurality of n-side contact regions may be arranged in a matrix of N rows and M columns where N≥3 and M≥3, centers of gravity of M n-side contact regions among the plurality of n-side contact regions may be on a straight line, the M n-side contact regions being disposed in each of first to N-th rows, centers of gravity of N n-side contact regions among the plurality of n-side contact regions may be on a straight line, the N n-side contact regions being disposed in each of first to M-th columns, in a unit enclosed by (i) a third straight line that divides equally a region between a first straight line and a second straight line, (ii) a fifth straight line that divides equally a region between the second straight line and a fourth straight line, (iii) an eighth straight line that divides equally a region between a sixth straight line and a seventh straight line, and (iv) a tenth straight line that divides equally a region between the seventh straight line and a ninth straight line, the first straight line connecting centers of gravity of the M n-side contact regions disposed in an i−1-th row where 2≤i≤N−1, the second straight line connecting centers of gravity of the M n-side contact regions disposed in an i-th row, the fourth straight line connecting centers of gravity of the M n-side contact regions disposed in an i+1-th row, the sixth straight line connecting centers of gravity of the N n-side contact regions disposed in an j−1-th column where 2≤j≤M−1, the seventh straight line connecting centers of gravity of the N n-side contact regions disposed in a j-th column, the ninth straight line connecting the centers of gravity of the N n-side contact regions disposed in a j+1-th column, the unit may include: a first unit corner portion between the third straight line and the eighth straight line; a second unit corner portion between the fifth straight line and the eighth straight line; a third unit corner portion disposed diagonally to the first unit corner portion; and a fourth unit corner portion disposed diagonally to the second unit corner portion, among the plurality of n-side contact regions, an n-side contact region disposed in the unit may include a first unit region extending in one direction from a first unit starting point that is spaced apart from the first unit corner portion, the first unit region having a linear shape, the p-side contact region may be disposed between the first unit starting point and the first unit corner portion, distance ru1that is a distance from the first unit corner portion and the first unit starting point may be less than or equal to 0.26 times length au1 of a shorter side of the unit, and among the plurality of n-side contact regions, n-side contact regions disposed in all of the units that satisfy 2≤i≤N−1, and 2≤j≤M−1 may include the first unit region.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, the n-side contact region disposed in the unit may include: a second unit region having a linear shape and extending in one direction from a second unit starting point that is spaced apart from the second unit corner portion; a third unit region having a linear shape and extending in one direction from a third unit starting point that is spaced apart from the third unit corner portion; and a fourth unit region having a linear shape and extending in one direction from a fourth unit starting point that is spaced apart from the fourth unit corner portion, the p-side contact region may be disposed between the second unit starting point and the second unit corner portion, between the third unit starting point and the third unit corner portion, and between the fourth unit starting point and the fourth unit corner portion, and distance rut between the second unit corner portion and the second unit starting point, distance ru3between the third unit corner portion and the third unit starting point, and distance ru4between the fourth unit corner portion and the fourth unit starting point may be each less than or equal to 0.26 times length au1 of the shorter side of the unit.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first n-side contact region, the second n-side contact region, the third n-side contact region, and the fourth n-side contact region may each have an X shape, and b≤0.10 may be satisfied where b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure.

In addition, in one aspect of the nitride semiconductor light-emitting element according to the present disclosure, in the plan view of the main surface, the first n-side contact region, the second n-side contact region, the third n-side contact region, and the fourth n-side contact region may each have a rectangular annular shape, and b≤0.07 may be satisfied where b denotes the proportion of an area of the n-side contact region to an area of the semiconductor stack structure.

Advantageous Effects

With the present disclosure, it is possible to provide a nitride semiconductor light-emitting element that is capable of reducing the forward voltage.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be noted that each of the embodiments described below shows a specific example of the present disclosure. Therefore, numerical values, shapes, materials, structural components, the arrangement and connection of the structural components, etc. indicated in the following embodiments are mere examples, and are not intended to limit the scope of the present disclosure.

In addition, each of the diagrams is a schematic diagram and thus is not necessarily strictly illustrated. Therefore, the scale sizes and the like are not necessarily exactly represented in each of the diagrams. In each of the diagrams, substantially the same structural components are assigned with the same reference signs, and redundant descriptions will be omitted or simplified.

Moreover, in the present specification, the terms “above” and “below” do not refer to the vertically upward direction and vertically downward direction in terms of absolute spatial recognition, but are used as terms defined by relative positional relationships based on the layering order in a layered configuration. Furthermore, the terms “above” and “below” are applied not only when two structural components are disposed with a gap therebetween or when a separate structural component is interposed between two structural components, but also when two structural components are disposed in close contact with each other or when two structural components come into contact with each other.

A nitride semiconductor light-emitting element according to Embodiment 1 will be described.

1-1. Overall Configuration

First, an overall configuration of a nitride semiconductor light-emitting element according to the present embodiment will be described with reference to the drawings.FIG.1is a diagram schematically illustrating the overall configuration of nitride semiconductor light-emitting element1according to the present embodiment.FIG.1illustrates plan view (a) and cross-sectional view (b) of nitride semiconductor light-emitting element1. Cross-sectional view (b) ofFIG.1illustrates a cross-section surface taken along line IB-IB indicated in plan view (a).

As illustrated inFIG.1, nitride semiconductor light-emitting element1includes: substrate11; semiconductor stack structure1s; n-side contact electrode15; p-side contact electrode16; insulating layer17; and cover electrode18. According to the present embodiment, nitride semiconductor light-emitting element1is a flip-chip light emitting diode (LED) in which semiconductor stack structure1s, n-side contact electrode15, and p-side contact electrode16are disposed on a main surface11aside of substrate11. Main surface11ais one of main surfaces of substrate11. Nitride semiconductor light-emitting element1, for example, emits light having a wavelength in the 450 nm band.

Substrate11is a plate-like component which serves as a base of nitride semiconductor light-emitting element1. As board11, for example, a light-transmissive substrate such as a sapphire substrate, a GaN substrate, etc. can be used.

Semiconductor stack structure1sis a stack structure including a plurality of semiconductor layers disposed above main surface11aof substrate11. Semiconductor stack structure1sincludes n-type semiconductor layer12, active layer13, and p-type semiconductor layer14which are stacked in sequence above main surface11aof substrate11. Semiconductor stack structure1sincludes exposure portion12ein which n-type semiconductor layer12is exposed, as a result of removing a portion of p-type semiconductor layer14and active layer13disposed above n-type semiconductor layer12.

As illustrated in plan view (a) ofFIG.1, semiconductor stack structure1shas a rectangular shape in a plan view of main surface11aof substrate11. In other words, semiconductor stack structure1shas a rectangular outer edge. In the plan view of main surface11aof substrate11, semiconductor stack structure1sincludes first corner portion C1, second corner portion C2, third corner portion C3, and fourth corner portion C4.

N-type semiconductor layer12is a layer including an n-type semiconductor that is disposed above substrate11. N-type semiconductor layer12includes an n-type GaN-based semiconductor layer. N-type semiconductor layer12may include a plurality of layers such as n-type clad layers. As n-type semiconductor layer12, for example, an n-type AlGaN layer may be used. As an n-type dopant that is included in n-type semiconductor layer12, Si, Ge, etc. can be used.

Active layer13is a light-emitting layer disposed above n-type semiconductor layer12. According to the present embodiment, an InGaN-based semiconductor layer is used as active layer13. Active layer13may have a single-layer structure or have a quantum well structure.

P-type semiconductor layer14is a layer including a p-type semiconductor dispose above active layer13. P-type semiconductor layer14includes a p-type GaN-based semiconductor layer. P-type semiconductor layer14may include a plurality of layers such as p-type clad layers. As p-type semiconductor layer14, for example, a p-type AlGaN layer may be used. As a p-type dopant that is included in p-type semiconductor layer14, Mg, etc. can be used.

N-side contact electrode15is a conductive layer that is disposed above n-type semiconductor layer12and is in contact with n-type semiconductor layer12in n-side contact region40. N-side contact electrode15is disposed in exposure portion12ein which n-type semiconductor layer12is exposed. The configuration of n-side contact electrode15is not particularly limited as long as n-side contact electrode15is a conductive layer that makes ohmic contact with n-type semiconductor layer12. According to the present embodiment, n-side contact electrode15is a stack structure including an Al layer having a thickness of 0.3 μm, a Ti layer having a thickness of 0.3 μm, and an Au layer having a thickness of 1.0 μm, which are stacked in sequence from the n-type semiconductor layer12side.

N-side contact region40has an X shape in the plan view of main surface11aof substrate11, as illustrated in plan view (a) ofFIG.1. The detailed configuration of n-side contact region40will be described below.

P-side contact electrode16is a conductive layer that is disposed above p-type semiconductor layer14, and in contact with p-type semiconductor layer14in p-side contact region60. The configuration of p-side contact electrode16is not particularly limited as long as p-side contact electrode16is a conductive layer that makes ohmic contact with p-type semiconductor layer14. According to the present embodiment, p-side contact electrode16is a stack structure including an Ag layer having a thickness of 0.2 μm, a Ti layer having a thickness of 0.7 μm, and an Au layer having a thickness of 0.3 μm, which are stacked in sequence above p-type semiconductor layer14. The Ag layer is a reflective metal that makes ohmic contact with p-type semiconductor layer14, and reflects light generated in active layer13. The Ti layer and the Au layer are barrier electrodes that cover the Ag layer.

Insulating layer17is a layer that comprises an insulating material. Insulating layer17covers continuously a portion of exposure portion12ein which n-type semiconductor layer12is exposed and a portion above p-type semiconductor layer14. Insulating layer17may include an opening portion defined above exposure portion12e. The configuration of insulating layer17is not particularly limited as long as insulating layer17is a layer that comprises an insulating material. According to the present embodiment, insulating layer17is a layer that comprises SiO2and has a thickness of 1.0 μm.

Cover electrode18is an electrode that covers p-side contact electrode16. The configuration of cover electrode18is not particularly limited as long as cover electrode18is a conductive film. According to the present embodiment, cover electrode18is a stack structure including an Al layer having a thickness of 0.3 μm, a Ti layer having a thickness of 0.3 μm, and an Au layer having a thickness of 1.0 μm, which are stacked in sequence so as to cover p-side contact electrode16. It should be noted that cover electrode18may have the configuration equivalent to the configuration of n-side contact electrode15.

Next, a mounting aspect of nitride semiconductor light-emitting element1according to the present embodiment will be described.FIG.2is a cross sectional view schematically illustrating one example of the mounting aspect of nitride semiconductor light-emitting element1according to the present embodiment.

As illustrated inFIG.2, in one example of the mounting aspect of nitride semiconductor light-emitting element1according to the present embodiment, nitride semiconductor light-emitting element1is flip-chip mounted on mounting substrate25. In other words, nitride semiconductor light-emitting element1is mounted on mounting substrate25in an orientation such that semiconductor stack structure1sfaces mounting substrate25.

Mounting substrate25is a substrate on which nitride semiconductor light-emitting element1is mounted, and n-side wiring electrode23and p-side wiring electrode24are disposed on a main surface of mounting substrate25on which nitride semiconductor light-emitting element1is mounted. The configuration of mounting substrate25is not particularly limited. According to the present embodiment, mounting substrate25is a ceramic substrate comprising an AlN sintered body.

N-side wiring electrode23and p-side wiring electrode24are conductive layers disposed on mounting substrate25. N-side wiring electrode23and p-side wiring electrode24are insulated from each other. The configuration of each of n-side wiring electrode23and p-side wiring electrode24is not particularly limited as long as n-side wiring electrode23and p-side wiring electrode24are conductive layers. According to the present embodiment, each of n-side wiring electrode23and p-side wiring electrode24comprises Au.

Seed metal26and p-side connecting member22are disposed in sequence from the cover electrode18side between cover electrode18and p-side wiring electrode24. Seed metal26and n-side connecting member21are disposed in sequence from the n-side contact electrode15side between n-side contact electrode15and n-side wiring electrode23.

Seed metal26is a metal layer disposed above cover electrode18and n-side contact electrode15, and serves as a base for p-side connecting member22and n-side connecting member21. The configuration of seed metal26is not particularly limited as long as seed metal26is a metal layer that serves as a base for p-side connecting member22and n-side connecting member21. According to the present embodiment, seed metal26is a stack structure in which a Ti layer having a thickness of 0.1 μm and an Au layer having a thickness of 0.3 μm are stacked in sequence from the semiconductor stack structure1sside.

P-side connecting member22is a conductive member that connects seed metal26and p-side wiring electrode24. N-side connecting member21is a conductive member that connects seed metal26and n-side wiring electrode23. P-side connecting member22and n-side connecting member21are not particularly limited as long as p-side connecting member22and n-side connecting member21are conductive members. P-side connecting member22and n-side connecting member21may be conductive members with high thermal conductivity. With this configuration, it is possible to facilitate heat discharge from nitride semiconductor light-emitting element1to mounting substrate25. P-side connecting member22and n-side connecting member21are, for example, bumps that comprise Au. It should be noted that p-side connecting member22and n-side connecting member21may be, for example, any one of Au, Ag, Al, or Cu, or an alloy of a combination of them.

Nitride semiconductor light-emitting element1is mounted on mounting substrate25as described above. With the configuration as described above, an electric current is supplied to nitride semiconductor light-emitting element1from the mounting substrate25side, and light generated in active layer13is emitted from the substrate11side of nitride semiconductor light-emitting element1.

1-3. Manufacturing Method

Next, the manufacturing method of nitride semiconductor light-emitting element1according to the present embodiment will be described with reference toFIG.3toFIG.6.FIG.3toFIG.6are cross sectional views schematically illustrating the processes of a manufacturing method of nitride semiconductor light-emitting element1according to the present embodiment.

First, as illustrated inFIG.3, substrate11is prepared, and semiconductor stack structure1sis stacked on main surface11athat is one of the main surfaces of substrate11. According to the present embodiment, n-type semiconductor layer12that includes an n-type GaN-based semiconductor layer, active layer13that includes an InGaN-based semiconductor layer, and p-type semiconductor layer14that includes a p-type GaN-based semiconductor layer are stacked in stated order above main surface11athat is one of the main surfaces of substrate11comprising a sapphire substrate or a GaN substrate, using an epitaxial growth technique by the metal organic chemical vapor deposition (MOCVD) method. Then, portions of p-type semiconductor layer14, active layer13, and n-type semiconductor layer12are removed to form exposure portion12ewhich is a recess in which n-type semiconductor layer12is exposed. According to the present embodiment, dry etching is used to remove the portions of p-type semiconductor layer14, active layer13, and n-type semiconductor layer12.

Then, as illustrated inFIG.4, a p-side contact electrode16having a predetermined shape is formed above p-type semiconductor layer14. According to the present embodiment, photolithography technique is used to form a resist pattern provided with an opening in the region in which p-type semiconductor layer14is disposed. Then, an Ag film having a thickness of 0.2 μm is deposited by the sputtering method, and the resist and Ag on the resist are removed by the lift-off method to form an Ag layer as a reflective metal patterned in a predetermined shape. Then, a stacked film including a Ti film having a thickness of 0.7 μm and an Au film having a thickness of 0.3 μm, which cover the Ag layer, is deposited by the sputtering method. Then, a resist pattern that covers p-type semiconductor layer14is formed by the photolithography technique, an excess portion of the stacked film formed in a region other than the region above p-type semiconductor layer14is removed by wet etching, and the resist is removed by organic cleaning. In this manner, p-side contact electrode16including the Ag layer, the Ti layer, and the Au layer is formed. Here, the outer edge of p-side contact electrode16and the outer edge of semiconductor stack structure1sare spaced apart from each other with a gap of 8 μm, for example. In addition, the edge of p-side contact electrode16on the n-side contact electrode side and the edge of exposure portion12eare spaced apart with a gap of 8 μm, for example.

Then, as illustrated inFIG.5, insulating layer17is formed. According to the present embodiment, an oxide film that comprises SiO2and has a thickness of 1.0 μm is deposited on the entire surface above semiconductor stack structure1sand p-side contact electrode16. Then, a resist pattern is formed in which portions of n-type semiconductor layer12and p-type semiconductor layer14are opened, and the resist is removed after the oxide film in the region in which the resist pattern is not formed is removed by wet etching. In this manner, insulating layer17in which the portion above exposure portion12eand the portion above p-side contact electrode16of the oxide film are removed is formed.

Then, as illustrated inFIG.6, n-side contact electrode15having a predetermined shape and cover electrode18are simultaneously formed in a region in which insulating layer17is not disposed in exposure portion12eand a region above p-type semiconductor layer14, respectively. According to the present embodiment, a resist pattern is formed to cover the region between p-type semiconductor layer14and the region in which n-side contact electrode15is formed, and a stacked film including an Al film having a thickness of 0.3 μm, a Ti film having a thickness of 0.3 μm, and an Au film having a thickness of 1.0 μm is formed using an electron beam (EB) deposition method. Then, n-side contact electrode15including an Al layer, a Ti layer, and an Au layer and cover electrode18are formed by removing the resist and the stacked film above the resist by the lift-off method.

As described above, nitride semiconductor light-emitting element1according to the present embodiment can be manufactured.

1-4. Detailed Configuration of N-Side Contact Region40

Next, the detailed configurations of n-side contact region40and p-side contact region60of nitride semiconductor light-emitting element1according to the present embodiment will be described with reference toFIG.7.FIG.7is a plan view illustrating the configurations of n-side contact region40and p-side contact region60according to the present embodiment. It should be noted that the following describes the configurations of n-side contact region40, etc. in a plan view of main surface11aof substrate11.

As illustrated inFIG.7, in nitride semiconductor light-emitting element1according to the present embodiment, in a plan view of main surface11aof substrate11, semiconductor stack structure1shas a rectangular shape, and includes first corner portion C1, second corner portion C2, third corner portion C3, and fourth corner portion C4respectively corresponding to the four vertexes of the rectangular shape. Second corner portion C2is a corner portion adjacent to first corner portion C1. In other words, second corner portion C2is a corner portion disposed on the same side of a rectangular outer edge of semiconductor stack structure1sas first corner portion C1. Third corner portion C3is a corner portion disposed diagonally to first corner portion C1. Fourth corner portion C4is a corner portion disposed diagonally to second corner portion C2.

N-side contact region40includes first region41. According to the present embodiment, n-side contact region40further includes second region42. First region41is a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42is a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Here, a linear region means a stripe-shaped region having a certain width extending along a straight line. The ratio of the length direction to the width of the linear region is greater than or equal to 2, for example. The edge of the linear region may have, for example, a rectangular shape or a semicircular shape.

P-side contact region60is disposed between first starting point S1and first corner portion C1, and between second starting point S2and second corner portion C2. It should be noted that no n-side contact region40is disposed between first starting point S1and first corner portion C1, and between second starting point S2and second corner portion C2.

Distance r1between first corner portion C1and first starting point S1is less than or equal to 0.26 times length a of a shorter side of semiconductor stack structure1sin a plan view of main surface11aof substrate11. Here, the shorter side of semiconductor stack structure1smeans the shorter two of the four sides of the rectangular outer edge of semiconductor stack structure1sin a plan view. The shape of semiconductor stack structure1sin a plan view is square according to the present embodiment. In addition, according to the present embodiment, distance r2between second corner portion C2and second starting point S2is less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin a plan view of main surface11aof substrate11.

According to the present embodiment, first region41linearly extends from first starting point S1to third starting point S3. Third starting point S3is a starting point that is spaced apart from third corner portion C3. Second region42linearly extends from second starting point S2to fourth starting point S4. Fourth starting point S4is a starting point that is spaced apart from fourth corner portion C4. First region41and second region42intersect. In other words, n-side contact region40has an X shape.

According to the present embodiment, distance r3between third corner portion C3and third starting point S3and distance r4between fourth corner portion C4and fourth starting point S4are each less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin a plan view of main surface11aof substrate11. It should be noted that distances r1, r2, r3, and r4are not particularly limited as long as distances r1, r2, r3, and r4are each less than or equal to 0.26 times length a of the shorter side. According to the present embodiment, distances r1, r2, r3, and r4are equal to one another.

P-side contact region60is disposed between third starting point S3and third corner portion C3and between fourth starting point S4and fourth corner portion C4. It should be noted that no n-side contact region40is disposed between third starting point S3and third corner portion C3and between fourth starting point S4and fourth corner portion C4.

1-5. Function and Advantageous Effect

Next, a function and an advantageous effect of nitride semiconductor light-emitting element1according to the present embodiment will be described with reference toFIG.8.FIG.8is a diagram illustrating the relationship between each position of the p-side contact region and the distance from the position to the n-side contact region, in each of the nitride semiconductor light-emitting element according to a comparison example and nitride semiconductor light-emitting element1according to the present embodiment. Graphs (a) and (b) illustrated inFIG.8each indicate the relationship between each position of the p-side contact region and the distance from the position to the n-side contact region in a plan view of the main surface of the substrate of the nitride semiconductor light-emitting element according to a comparison example and nitride semiconductor light-emitting element1according to the present embodiment. The shaded hatched region in each of the graphs indicates the n-side contact region, and almost the entire area other than the n-side contact region corresponds to the p-side contact region. In each of the graphs inFIG.8, the region with the larger distance is represented in darker gray.

The nitride semiconductor light-emitting element according to the comparison example includes a semiconductor stack structure having a rectangular shape in a plan view of the main surface of the substrate as with nitride semiconductor light-emitting element1according to the present embodiment. In nitride semiconductor light-emitting element according to the comparison example, the outer edge of the n-side contact region is circular, as indicated in graph (a) ofFIG.8. In the nitride semiconductor light-emitting element according to the comparison example including such an n-side contact region, the distance between the position in proximity to the corner portion of the semiconductor stack structure in the p-side contact region and the n-side contact region becomes large. Since it is necessary for the current injected into the light-emitting layer at this position to travel this distance in the n-type layer in the planar direction, the electrical resistance of the nitride semiconductor light-emitting element according to the comparison becomes large. As a result, the forward voltage becomes high in the nitride semiconductor light-emitting element according to the comparison example.

On the other hand, in nitride semiconductor light-emitting element1according to the present embodiment, as indicated in graph (b) ofFIG.8, n-side contact region40includes first region41that linearly extends from the position in proximity to the corner portion of semiconductor stack structure1s. Accordingly, it is possible to reduce the distance from the corner portion of semiconductor stack structure1sto n-side contact region40, in p-side contact region60. As a result, it is possible to reduce the electrical resistance between the corner portion of semiconductor stack structure1sand n-side contact region40, in p-side contact region60. This enables reduction in the forward voltage in nitride semiconductor light-emitting element1according to the present embodiment. In addition, according to the present embodiment, as described above, since the distance from each of first corner portion C1, second corner portion C2, third corner portion C3, and fourth corner portion C4to n-side contact region40is less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1s, it is possible to reduce the distance from the position in proximity to each of the four corner portions of semiconductor stack structure1sto n-side contact region40, in p-side contact region60. As a result, with nitride semiconductor light-emitting element1according to the present embodiment, it is possible to further reduce the forward voltage.

The forward voltage in nitride semiconductor light-emitting element1according to the present embodiment will be described with reference toFIG.9.FIG.9is a graph indicating the relationship between forward voltage Vf and ratio r/a. Ratio r/a is the ratio of distance r from each of the corner portions to n-side contact region40to length a of the shorter side of nitride semiconductor light-emitting element1according to the present embodiment. The horizontal axis of the graph inFIG.9indicates ratio r/a and the vertical axis indicates forward voltage Vf.

In the graph illustrated inFIG.9, the experimental results of forward voltage Vf when (i) distance r1between first corner portion C1and first starting point S1, distance r2between second corner portion C2and second starting point S2, distance r3between third corner portion C3and third starting point S3, and distance r4between fourth corner portion C4and fourth starting point S4are equal to one another, and (ii) proportion b is 0.2 are indicated. Proportion b is a proportion of the area of n-side contact region40to the area of semiconductor stack structure1sin a plane view of main surface11aof substrate11. In this experiment, ratio r/a, etc. are varied under the condition that the widths of first region41and second region42are equal to each other. Distances r from the corner portions to n-side contact region40respectively correspond to distances r1, r2, r3and r4. Forward voltage Vf represents the forward voltage when the supply current is 1 A for nitride semiconductor light-emitting element1with the shorter side and the longer side being the same 1 mm.

As indicated schematically in the graph ofFIG.9, as ratio r/a on the horizontal axis becomes smaller, each region of n-side contact region40(i.e., first region41and second region42) becomes narrower and longer, and as ratio r/a becomes greater, each region of n-side contact region40becomes wider and shorter. When ratio r/a is approximately 0.48, the shape of n-side contact region40is not an X but a rectangle, and thus forward voltage Vf of the case where ratio r/a is approximately less than or equal to 0.48 is indicated inFIG.9.

As illustrated inFIG.9, forward voltage Vf is a minimal value of approximately 3.5 V when ratio r/a is approximately 0.14, and is close to a minimal value of less than 3.6 V when ratio r/a is greater than 0 and less than or equal to 0.26. On the other hand, in the nitride semiconductor light-emitting element of the above-described comparative example (graph (a) inFIG.8), forward voltage Vf is greater than or equal to 3.8 V.

As described above, in nitride semiconductor light-emitting element1according to the present embodiment, ratio r/a is greater than 0 and less than or equal to 0.26, and thus it is possible to reduce forward voltage Vf compared to the nitride semiconductor light-emitting element according to the comparison example. With nitride semiconductor light-emitting element1according to the present embodiment, it is possible to reduce forward voltage Vf, and thus the loss component that is included in forward voltage Vf and does not contribute to light emission can be reduced. As a result, with nitride semiconductor light-emitting element1according to the present embodiment, it is possible to increase the utilization efficiency of power and reduce heat generation due to the loss component. In addition, since heat generation can be reduced, it is possible to enhance the performance and reliability of nitride semiconductor light-emitting element1.

Next, the relationship between forward voltage Vf and proportion b of the area of n-side contact region40to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1according to the present embodiment will be described with reference toFIG.10.FIG.10is a graph indicating the relationship between normalized forward voltage Vf and ratio r/a. Ratio r/a is the ratio of distance r from each of the corner portions to n-side contact region40to length a of the shorter side of nitride semiconductor light-emitting element1according to the present embodiment. The horizontal axis of the graph inFIG.10indicates ratio r/a and the vertical axis indicates normalized forward voltage Vf. InFIG.10, the experimental results when proportion b is 0.1, 0.2, and 0.3 are indicated by a circle, a square, and a triangle, respectively. Normalized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf when the ratio r/a is 0.

As illustrated inFIG.10, normalized forward voltage Vf has a minimal value in the range in which ratio r/a is greater than 0 and less than or equal to 0.26 for each of the cases where proportion b of the area of n-side contact region40is 0.1, 0.2, and 0.3.

The maximum value of ratio r/a indicated inFIG.10is ratio r/a when n-side contact region40has a rectangular shape instead of an X shape. Here, the range of ratio r/a which allows normalized forward voltage Vf to be smaller than in the case where ratio r/a is at the maximum will be considered. As illustrated inFIG.10, in the range where ratio r/a is greater than 0 and less than or equal to the maximum value, normalized forward voltage Vf is at the maximum when ratio r/a is at the maximum for any proportion b of the area of n-side contact region40. Accordingly, when ratio r/a is less than these maximum values, normalized forward voltage Vf can be smaller than in the case where ratio r/a is at the maximum. As illustrated inFIG.10, when proportion b is 0.1, 0.2, and 0.3, the maximum values of ratio r/a are approximately 0.55, 0.48, and 0.43, respectively, and the maximum value of ratio r/a is greater than 0.26 in any of the cases. Accordingly, in the case where proportion b is greater than or equal to 0.1 and less than or equal to 0.3, normalized forward voltage Vf can be smaller than in the case where ratio r/a is at the maximum when ratio r/a is less than or equal to 0.26. It should be noted that, although the experimental results for the case where proportion b is less than 0.1 are not shown, the maximum value of ratio r/a is greater when proportion b is less than 0.1 than in the case where proportion b is 0.1. Accordingly, in the case where proportion b is less than 0.1, normalized forward voltage Vf can also be smaller than in the case where ratio r/a is at the maximum when ratio r/a is less than or equal to 0.26. In view of the above, in the case where proportion b is less than or equal to 0.3 and ratio r/a is less than or equal to 0.26, normalized forward voltage Vf can be smaller than in the case where ratio r/a is at the maximum.

Next, the range of ratio r/a which allows normalized forward voltage Vf as indicated inFIG.10to be less than 1 will be considered. As illustrated inFIG.10, normalized forward voltage Vf is 1 when ratio r/a is 0, and normalized forward voltage Vf is less than 1 in the range in which ratio r/a is greater than 0 and less than a predetermined value. Here, the maximum value of the range of ratio r/a in which normalized forward voltage Vf is less than 1 will be explained with reference to FIG.11.

FIG.11is a graph indicating the relationship between proportion b of the area of n-side contact region40to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1according to the present embodiment and the maximum value of ratio r/a which allows normalized forward voltage Vf to be less than 1. The horizontal axis of the graph inFIG.11indicates proportion b, and the vertical axis indicates ratio r/a. InFIG.11, the maximum value of ratio r/a which allows normalized forward voltage Vf to be less than 1 is indicated by a triangle. It should be noted that ratio r/a in the case where normalized forward voltage Vf has a minimal value is also indicated by a square inFIG.11.

As illustrated inFIG.11, when the relationship between proportion b and the maximum value of ratio r/a which allows normalized forward voltage Vf to be less than 1 is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (1) when b is less than or equal to 0.3.

Accordingly, distances r1to r4, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (2) to (4).

This allows forward voltage Vf of nitride semiconductor light-emitting element1to be less than forward voltage Vf of the case where ratio r/a is 0.

Next, the relationship between a light emission output and proportion b of the area of n-side contact region40to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1will be described with reference toFIG.12.FIG.12is a graph indicating the relationship between (i) proportion b of the area of n-side contact region40to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1according to the present embodiment and (ii) the ratio of the light emission output of nitride semiconductor light-emitting element1according to the present embodiment in the case where ratio r/a is the ratio when normalized forward voltage Vf has a minimal value to the light emission output of the nitride semiconductor light-emitting element according to the comparison example.FIG.12is a graph indicating the experimental results. The horizontal axis of the graph indicates proportion b and the vertical axis indicates the ratio of the light emission output.

As illustrated inFIG.12, the ratio of the light emission output is greater than 1 in the entire range in which proportion b is less than or equal to 0.3. In other words, nitride semiconductor light-emitting element1according to the present embodiment has a greater light emission output than the nitride semiconductor light-emitting element according to the comparison example. In addition, as proportion b decreases from 0.3 to 0.1, the ratio of the light emission output increases substantially linearly, and as proportion b decreases further from 0.1, the ratio of the light emission output increases more steeply than linearly. Accordingly, in nitride semiconductor light-emitting element1according to the present embodiment, proportion b may satisfy b≤0.10. In this manner, it is possible to further increase the light emission output of nitride semiconductor light-emitting element1compared to the light emission output of the nitride semiconductor light-emitting element of the comparison example.

Next, a nitride semiconductor light-emitting element according to Variation 1 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1according to Embodiment 1 in points other than that the n-side contact region includes four regions which are not connected one another. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1according to Embodiment 1.

First, the configuration of an n-side contact region of the nitride semiconductor light-emitting element according to the present variation will be described with reference toFIG.13.FIG.13is a plan view schematically illustrating the configuration of n-side contact region40aof nitride semiconductor light-emitting element1aaccording to the present variation.FIG.13illustrates n-side contact region40ain a plan view of main surface11aof substrate11.

As illustrated inFIG.13, n-side contact region40aaccording to the present variation includes first region41a, second region42a, third region43a, and fourth region44a. First region41ais a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42ais a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43ais a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44ais a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

In the present variation, distance r1between first corner portion C1and first starting point Si, distance r2between second corner portion C2and second starting point S2, distance r3between third corner portion C3and third starting point S3, and distance r4between fourth corner portion C4and fourth starting point S4are each less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin the plan view of main surface11aof substrate11. It should be noted that distances r1, r2, r3, and r4are not particularly limited as long as distances r1, r2, r3, and r4are each less than or equal to 0.26 times length a of the shorter side. According to the present variation, distances r1, r2, r3, and r4are equal to one another.

Third region43ais disposed on the extended line of first region41aand spaced apart from first region41a, and fourth region44ais disposed on the extended line of second region42aand spaced apart from second region42a.

First region41a, second region42a, third region43a, and fourth region44aare disposed to be spaced apart from one another.

First region41aand third region43aextend in the same direction, and second region42aand fourth region44aextend in the same direction.

The extended line of first region41aintersects the extended line of second region42a. The extended line of second region42aintersects the extended line of third region43a. The extended line of third region43aintersects the extended line of fourth region44a. The extended line of fourth region44aintersects the extended line of first region41a.

It should be noted that, since nitride semiconductor light-emitting element1aaccording to the present variation includes n-side contact region40athat is different from that of Embodiment 1, the configurations of n-side contact electrode15, p-side contact region60, p-side contact electrode16, and cover electrode18are also different from those of nitride semiconductor light-emitting element1according to Embodiment 1. In the plan view of main surface11aof substrate11, the shape of n-side contact electrode15is similar to the shape of n-side contact region40a, and p-side contact region60and p-side contact electrode16are disposed substantially in the entire region of semiconductor stack structure1sother than the region in which n-side contact region is disposed. Cover electrode18is disposed above p-side contact electrode16. Although the description will be omitted below, in each of the following variations and in each of the following embodiments, the configuration of the other components can also be changed according to the configuration of the n-side contact region.

With nitride semiconductor light-emitting element1aaccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, the relationship between (i) d5which is half the distance between first region41aand third region43aindicated inFIG.13, (ii) d6which is half the distance between second region42aand fourth region44aindicated inFIG.13, and (iii) forward voltage Vf will be described with reference toFIG.14. It should be noted that, in the following description, the experimental results in the case where: d5=d6=d; r1=r2=r3=r4; and ratio r1/a is the ratio when normalized forward voltage Vf has a minimal value (indicated by the squares inFIG.11) will be described.FIG.14is a graph indicating the relationship between ratio d/a and normalized forward voltage Vf in nitride semiconductor light-emitting element1aaccording to the present variation. It should be noted that the horizontal axis of the graph inFIG.14indicates ratio d/a and the vertical axis indicates normalized forward voltage Vf. InFIG.14, the experimental results when proportion b is 0.1, 0.2, and 0.3 are indicated by a circle, a square, and a triangle, respectively. Normalized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf of the case where ratio d/a is 0. In this experiment, ratio d/a, etc. were varied under the condition that the area of n-side contact region40ais equal and the width of each region is equal.

As indicated schematically in the graph ofFIG.14, as ratio d/a on the horizontal axis becomes smaller, each region of n-side contact region40abecomes narrower and longer, and as ratio d/a increases, each region of n-side contact region40abecomes wider and shorter.

Here, the range of ratio d/a which allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum (i.e., a limit value for the width of each region to be placeable in proximity to a corresponding one of the corner portions) will be considered. As indicated inFIG.14, for any value of proportion b, normalized forward voltage Vf is at the maximum when ratio d/a is at the maximum. For example, as indicated by the arrow inFIG.14, when proportion b is 0.3, the maximum value of ratio d/a is approximately 0.42, and when ratio d/a is less than 0.42, normalized forward voltage Vf is smaller than in the case where ratio d/a is at the maximum. As described above, when ratio d/a is less than the maximum value, it is possible to reduce the forward voltage compared to the case where ratio d/a is at the maximum.

The range of the value of ratio d/a that allows forward voltage Vf to be less than in the case where ratio d/a indicated inFIG.14is at the maximum will be described with reference toFIG.15.FIG.15is a graph indicating the relationship between the maximum value of ratio d/a and proportion b of the area of n-side contact region40ato the area of semiconductor stack structure is of nitride semiconductor light-emitting element1aaccording to the present variation. The horizontal axis of the graph inFIG.15indicates proportion b, and the vertical axis indicates ratio d/a. InFIG.15, the maximum value of ratio d/a is indicated by a triangle.

As illustrated inFIG.15, when the relationship between proportion b and the maximum value of ratio d/a is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (5) when b is less than or equal to 0.3.

Accordingly, distances d5and d6, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (6) to (8).

This allows forward voltage Vf of nitride semiconductor light-emitting element1ato be less than forward voltage Vf of the case where ratio d/a is at the maximum.

Next, the range of ratio d/a which allows normalized forward voltage Vf as indicated inFIG.14to be less than or equal to 1 will be considered. As illustrated inFIG.14, normalized forward voltage Vf is 1 when ratio d/a is 0, and normalized forward voltage Vf is less than or equal to 1 in the range in which ratio d/a is greater than 0 and less than or equal to a predetermined value. Here, the maximum value of the range of ratio d/a in which the normalized forward voltage Vf is less than or equal to 1 will be explained with reference toFIG.16.

FIG.16is a graph indicating the relationship between proportion b of the area of n-side contact region40ato the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1aaccording to the present variation and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1. The horizontal axis of the graph inFIG.16indicates proportion b, and the vertical axis indicates ratio d/a. InFIG.16, the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is indicated by a diamond.

As illustrated inFIG.16, when the relationship between proportion b and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (9) when b is less than or equal to 0.3.

Accordingly, distances d5and d6, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (10) to (12).

This allows forward voltage Vf of nitride semiconductor light-emitting element1bto be less than forward voltage Vf of the case where ratio d/a is 0.

Next, a nitride semiconductor light-emitting element according to Variation 2 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1 in points other than that the n-side contact region includes six regions. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1.

First, the configuration of an n-side contact region of the nitride semiconductor light-emitting element according to the present variation will be described with reference toFIG.17.FIG.17is a plan view schematically illustrating the configuration of n-side contact region40bof nitride semiconductor light-emitting element1baccording to the present variation.FIG.17illustrates n-side contact region40bin a plan view of main surface11aof substrate11.

As illustrated inFIG.17, n-side contact region40baccording to the present variation includes first region41b, second region42b, third region43b, fourth region44b, fifth region45b, and sixth region46b. First region41bis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42bis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43bis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44bis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Fifth region45bis a linear region which is disposed between first region41band third region43b, and is spaced apart from each of first region41band third region43b. According to the present variation, fifth region45bextends in the same direction as first region41band third region43b.

Sixth region46bis a linear region which is disposed between second region42band fourth region44b, and is spaced apart from each of second region42band fourth region44b. According to the present variation, sixth region46bextends in the same direction as second region42band fourth region44b.

In the present variation, distance r1between first corner portion C1and first starting point S1, distance r2between second corner portion C2and second starting point S2, distance r3between third corner portion C3and third starting point S3, and distance r4between fourth corner portion C4and fourth starting point S4are each less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin the plan view of main surface11aof substrate11. It should be noted that distances r1, r2, r3, and r4are not particularly limited as long as distances r1, r2, r3, and r4are each less than or equal to 0.26 times length a of the shorter side. According to the present variation, distances r1, r2, r3, and r4are equal to one other.

Third region43bis disposed on the extended line of first region41band spaced apart from first region41b, and fourth region44bis disposed on the extended line of second region42band spaced apart from second region42b.

First region41b, second region42b, third region43b, and fourth region44bare disposed to be spaced apart from one another.

First region41band third region43bextend in the same direction, and second region42band fourth region44bextend in the same direction.

The extended line of first region41bintersects the extended line of second region42b. The extended line of second region42bintersects the extended line of third region43b. The extended line of third region43bintersects the extended line of fourth region44b. The extended line of fourth region44bintersects the extended line of first region41b.

With nitride semiconductor light-emitting element1baccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Here, the relationship between: distance d1between first region41band fifth region45b; distance d2between second region42band sixth region46b; distance d3between third region43band fifth region45b; distance d4between fourth region44band sixth region46b; and forward voltage Vf of nitride semiconductor light-emitting element1bwill be described with reference toFIG.18. It should be noted that, in the following description, the experimental results in the case where: d1=d2=d3=d4=d; r1=r2=r3=r4; and ratio r1/a is the ratio when normalized forward voltage Vf has a minimal value (indicated by the square inFIG.11) will be described.FIG.18is a graph indicating the relationship between ratio d/a and normalized forward voltage Vf, in nitride semiconductor light-emitting element1baccording to the present variation. It should be noted that the horizontal axis of the graph inFIG.18indicates ratio d/a and the vertical axis indicates normalized forward voltage Vf. InFIG.18, the experimental results when proportion b is 0.1, 0.2, and 0.3 are indicated by a circle, a square, and a triangle, respectively. Normalized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf of the case where ratio d/a is 0. In this experiment, ratio d/a, etc. were varied under the condition that the area of the n-side contact region is equal and that length L of each of first region41b, second region42b, third region43band fourth region44bis equal to ½ the length of each of fifth region45band sixth region46b.

As indicated schematically in the graph ofFIG.18, as ratio d/a on the horizontal axis decreases, each region of n-side contact region40bbecomes narrower and longer, and as ratio d/a increases, each region of n-side contact region40bbecomes wider and shorter. In addition, when distance d becomes larger than a certain value, the widths of first region41b, second region42b, third region43b, and fourth region44bcannot be equal to the widths of fifth region45band sixth region46b. In this case, the experiment was conducted under the condition that fifth region45band sixth region46bare wider than first region41b, second region42b, third region43b, and fourth region44b.

Here, the range of ratio d/a which allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum (i.e., a limit value for the width of each region to be placeable in proximity to a corresponding one of the corner portions) will be considered. As indicated inFIG.18, for any value of proportion b, normalized forward voltage Vf is at the maximum when ratio d/a is at the maximum. For example, as indicated by the arrow inFIG.18, when proportion b is 0.3, the maximum value of ratio d/a is approximately 0.33, and when ratio d/a is less than 0.33, normalized forward voltage Vf is smaller than in the case where ratio d/a is at the maximum value. As described above, when ratio d/a is less than the maximum value, it is possible to reduce the forward voltage than in the case where ratio d/a is at the maximum.

The range of the value of ratio d/a that allows forward voltage Vf to be less than in the case where ratio d/a is at the maximum as indicated inFIG.18will be described with reference toFIG.19.FIG.19is a graph indicating the relationship between the maximum value of ratio d/a and proportion b of the area of n-side contact region40bto the area of semiconductor stack structure1sof nitride semiconductor light-emitting element1baccording to the present variation. The horizontal axis of the graph inFIG.19indicates proportion b, and the vertical axis indicates ratio d/a. InFIG.19, the maximum value of ratio d/a is indicated by a diamond.

As illustrated inFIG.19, when the relationship between proportion b and the maximum value of ratio d/a is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (13) when b is less than or equal to 0.3.

Accordingly, distances d1to d4, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (14) to (16).

This allows forward voltage Vf of nitride semiconductor light-emitting element1bto be less than forward voltage Vf of the case where ratio d/a is at the maximum.

Next, the range of ratio d/a which allows normalized forward voltage Vf as indicated inFIG.18to be less than or equal to 1 will be considered. As illustrated inFIG.18, normalized forward voltage Vf is 1 when ratio d/a is 0, and normalized forward voltage Vf is less than or equal to 1 in the range in which ratio d/a is greater than 0 and less than or equal to a predetermined value. Here, the result of calculating the maximum value of ratio d/a that allows normalized forward voltage Vf to be less than or equal to 1 will be described with reference toFIG.20.FIG.20is a graph indicating the relationship between (i) proportion b of the area of n-side contact region40bto the area of semiconductor stack structure is of nitride semiconductor light-emitting element1baccording to the present variation and (ii) the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1. The horizontal axis of the graph inFIG.20indicates proportion b, and the vertical axis indicates ratio d/a. In FIG.20, the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is indicated by a diamond.

As illustrated inFIG.20, when the relationship between proportion b and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (17) when b is less than or equal to 0.3.

Accordingly, distances d1to d4, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (18) to (20).

This allows forward voltage Vf of nitride semiconductor light-emitting element1bto be less than forward voltage Vf of the case where ratio d/a is 0.

Next, a nitride semiconductor light-emitting element according to Variation 3 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1 in points other than that the n-side contact region includes four regions and that, among the four regions, the first region and the second region intersect. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1, with reference toFIG.21.

FIG.21is a plan view schematically illustrating the configuration of n-side contact region40cof nitride semiconductor light-emitting element1caccording to the present variation.FIG.21illustrates n-side contact region40cin a plan view of main surface11aof substrate11.

As illustrated inFIG.21, n-side contact region40caccording to the present variation includes first region41c, second region42c, third region43c, and fourth region44c. First region41cis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42cis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43cis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44cis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43cis disposed on the extended line of first region41cand spaced apart from first region41c, and fourth region44cis disposed on the extended line of second region42cand spaced apart from second region42c.

First region41cand third region43cextend in the same direction, and second region42cand fourth region44cextend in the same direction.

First region41cand second region42cintersect. Second region42cand the extended line of third region43cintersect. The extended line of third region43cand the extended line of fourth region44cintersect. The extended line of fourth region44cand first region41cintersect.

With nitride semiconductor light-emitting element1caccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 4 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1baccording to Variation 2 of Embodiment 1 in points other than that the n-side contact region includes 10 regions. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1baccording to Variation 2 of Embodiment 1, with reference toFIG.22.

FIG.22is a plan view schematically illustrating the configuration of n-side contact region40dof nitride semiconductor light-emitting element1daccording to the present variation.FIG.22illustrates n-side contact region40din a plan view of main surface11aof substrate11.

As illustrated inFIG.22, n-side contact region40daccording to the present variation includes first region41d, second region42d, third region43d, fourth region44d, fifth region45d, sixth region46d, seventh region51d, eighth region52d, ninth region53d, and tenth region54d. First region41dis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42dis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43dis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44dis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43dis disposed on the extended line of first region41dand spaced apart from first region41d, and fourth region44dis disposed on the extended line of second region42dand spaced apart from second region42d.

First region41dand third region43dextend in the same direction, and second region42dand fourth region44dextend in the same direction.

The extended line of first region41dand the extended line of second region42dintersect. The extended line of second region42dand the extended line of third region43dintersect. The extended line of third region43dand the extended line of fourth region44dintersect. The extended line of fourth region44dand the extended line of first region41dintersect.

Each of fifth region45d, seventh region51d, and ninth region53dis a linear region disposed between first region41dand third region43d, and is spaced apart from each of first region41dand third region43d. Seventh region51dis disposed between first region41dand fifth region45d, and is spaced apart from fifth region45d. Ninth region53dis disposed between third region43dand fifth region45d, and is spaced apart from fifth region45d. In other words, first region41d, seventh region51d, fifth region45d, ninth region53d, and third region43dare disposed in stated order on the diagonal line connecting first corner portion C1and third corner portion C3. According to the present variation, fifth region45d, seventh region51d, and ninth region53dextend in the same direction as first region41dand third region43d.

Each of sixth region46d, eighth region52d, and tenth region54dis a linear region disposed between second region42dand fourth region44d, and is spaced apart from each of second region42dand fourth region44d. Eighth region52dis disposed between second region42dand sixth region46d, and is spaced apart from sixth region46d. Tenth region54dis disposed between fourth region44dand sixth region46d, and is spaced apart from sixth region46d. In other words, second region42d, eighth region52d, sixth region46d, tenth region54d, and fourth region44dare disposed in stated order on the diagonal line connecting second corner portion C2and fourth corner portion C4. According to the present variation, sixth region46d, eighth region52d, and tenth region54dextend in the same direction as second region42dand fourth region44d.

With nitride semiconductor light-emitting element1daccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 5 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1 in points other than that the n-side contact region includes four regions, and that, among those four regions, the first region and the third region are connected, and the second region and the fourth region are connected. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1aaccording to Variation 1 of Embodiment 1, with reference toFIG.23.

FIG.23is a plan view schematically illustrating the configuration of n-side contact region40eof nitride semiconductor light-emitting element1eaccording to the present variation.FIG.23illustrates n-side contact region40ein a plan view of main surface11aof substrate11.

As illustrated inFIG.23, n-side contact region40eaccording to the present variation includes first region41e, second region42e, third region43e, and fourth region44e. First region41eis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42eis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43eis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44eis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43eis disposed on the extended line of first region41e, and first region41eand third region43eare connected. Fourth region44eis disposed on the extended line of second region42e, and second region42eand fourth region44eare connected.

According to the present variation, first region41eand third region43eextend in different directions, and second region42eand fourth region44eextend in different directions.

It should be noted that first region41eand third region43emay extend in the same direction, and second region42eand fourth region44emay extend in the same direction. In other words, the region of a combination of first region41eand third region43emay extend linearly, and the region of a combination of second region42eand fourth region44emay extended linearly. In this case, nitride semiconductor light-emitting element1eaccording to the present variation has the same configuration as nitride semiconductor light-emitting element1according to Embodiment 1.

First region41eand second region42eintersect. Second region42eand the extended line of third region43eintersect. The extended line of third region43eand the extended line of fourth region44eintersect. The extended line of fourth region44eand first region41eintersect.

With nitride semiconductor light-emitting element1eaccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 6 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1eaccording to Variation 5 of Embodiment 1 in points other than that the n-side contact region includes four regions, and that these four regions are connected at one point. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1eaccording to Variation 5 of Embodiment 1, with reference toFIG.24.

FIG.24is a plan view schematically illustrating the configuration of n-side contact region40fof nitride semiconductor light-emitting element1faccording to the present variation.FIG.24illustrates n-side contact region40fin a plan view of main surface11aof substrate11.

As illustrated inFIG.24, n-side contact region40faccording to the present variation includes first region41f, second region42f, third region43f, and fourth region44f. First region41fis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42fis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43fis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44fis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43fis disposed on the extended line of first region41f, and first region41fand third region43fare connected to each other. Fourth region44fis disposed on the extended line of second region42f, and second region42fand fourth region44fare connected to each other.

According to the present variation, first region41fand third region43fextend in different directions, and second region42fand fourth region44fextend in different directions. First region41f, second region42f, third region43f, and fourth region44fare connected at one point. Here, second region42fand fourth region44fmay extend in the same direction.

With nitride semiconductor light-emitting element1faccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 7 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1eaccording to Variation 5 of Embodiment 1 in points other than that the n-side contact region includes four regions, and that, among those four regions, the first region and the third region are spaced apart from each other, and the second region and the fourth region are spaced apart from each other. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1eaccording to Variation 5 of Embodiment 1, with reference toFIG.25.

FIG.25is a plan view schematically illustrating the configuration of n-side contact region40gof nitride semiconductor light-emitting element1gaccording to the present variation.FIG.25illustrates n-side contact region40gin a plan view of main surface11aof substrate11.

As illustrated inFIG.25, n-side contact region40gaccording to the present variation includes first region41g, second region42g, third region43g, and fourth region44g. First region41gis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42gis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43gis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44gis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43gis disposed on the extended line of first region41gand spaced apart from first region41g. Fourth region44gis disposed on the extended line of second region42gand spaced apart from second region42g.

According to the present variation, first region41gand third region43gextend in different directions, and second region42gand fourth region44gextend in different directions.

First region41gand second region42gintersect. Second region42gand the extended line of third region43gintersect. The extended line of third region43gand the extended line of fourth region44gintersect. The extended line of fourth region44gand first region41gintersect.

With nitride semiconductor light-emitting element1gaccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 8 of Embodiment 1 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element1faccording to Variation 6 of Embodiment 1 in points other than that the n-side contact region includes four regions, and that these four regions are spaced apart from one another. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element1faccording to Variation 6 of Embodiment 1, with reference to FIG.

FIG.26is a plan view schematically illustrating the configuration of n-side contact region40hof nitride semiconductor light-emitting element1haccording to the present variation.FIG.26illustrates n-side contact region40hin a plan view of main surface11aof substrate11.

As illustrated inFIG.26, n-side contact region40haccording to the present variation includes first region41h, second region42h, third region43h, and fourth region44h. First region41his a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region42his a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region43his a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region44his a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

Third region43his disposed on the extended line of first region41hand spaced apart from first region41h. Fourth region44his disposed on the extended line of second region42hand spaced apart from second region42h.

First region41hand third region43hextend in different directions, and second region42hand fourth region44hextend in different directions. Here, second region42hand fourth region44hmay extend in the same direction.

First region41h, second region42h, third region43h, and fourth region44hare spaced apart from each other.

With nitride semiconductor light-emitting element1haccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

A nitride semiconductor light-emitting element according to Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present embodiment matches nitride semiconductor light-emitting element1according to Embodiment 1 in points other than that the n-side contact region has a rectangular annular shape. The following describes the nitride semiconductor light-emitting element according to the present embodiment focusing on the differences from nitride semiconductor light-emitting element1according to Embodiment 1.

2-1. Detailed Configuration of N-Side Contact Region140

First, the detailed configuration of an n-side contact region included in the nitride semiconductor light-emitting element according to the present embodiment will be described with reference toFIG.27.FIG.27is a plan view schematically illustrating the configuration of n-side contact region140of nitride semiconductor light-emitting element101according to the present embodiment.FIG.27illustrates a plan view of main surface11aof substrate11.

As illustrated inFIG.27, in nitride semiconductor light-emitting element101according to the present embodiment, in the plan view of main surface11aof substrate11, semiconductor stack structure1shas a rectangular shape, and includes first corner portion C1, second corner portion C2, third corner portion C3, and fourth corner portion C4respectively corresponding to the four vertexes of the rectangular shape.

N-side contact region140has a rectangular annular shape. More specifically, n-side contact region140includes first region141, second region142, third region143, and fourth region144. First region141is a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region142is a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region143is a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region144is a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

A p-side contact region is disposed between first starting point S1and first corner portion C1, between second starting point S2and second corner portion C2, between third starting point S3and third corner portion C3, and between fourth starting point S4and fourth corner portion C4. It should be noted that no n-side contact region140is disposed between first starting point S1and first corner portion C1, between second starting point S2and second corner portion C2, between third starting point S3and third corner portion C3, and between fourth starting point S4and fourth corner portion C4.

Distance r1between first corner portion C1and first starting point S1, distance r2between second corner portion C2and second starting point S2, distance r3between third corner portion C3and third starting point S3, and distance r4between fourth corner portion C4and fourth starting point S4are each less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin a plan view of main surface11aof substrate11. It should be noted that distances r1, r2, r3, and r4are not particularly limited as long as distances r1, r2, r3, and r4are each less than or equal to 0.26 times length a of the shorter side. According to the present embodiment, distances r1, r2, r3, and r4are equal to one another.

According to the present embodiment, first region141linearly extends from first starting point S1to second starting point S2. According to this configuration, first region141and second region142are connected to each other. Second region142linearly extends from second starting point S2to third starting point S3. According to this configuration, second region142and third region143are connected to each other. Third region143linearly extends from third starting point S3to fourth starting point S4. According to this configuration, third region143and fourth region144are connected to each other. Fourth region144linearly extends from fourth starting point S4to first starting point S1. According to this configuration, fourth region144and first region141are connected to each other. It should be noted that, in n-side contact region140according to the present embodiment, first region141may be identified as linearly extending from second starting point S2to first starting point S1. Second region142may be identified as linearly extending from third starting point S3to second starting point S2. Third region143may be identified as linearly extending from fourth starting point S4to third starting point S3. Fourth region144may be identified as linearly extending from first starting point S1to fourth starting point S4. Furthermore, two regions, namely, first region141and second region142, may be identified as linearly extending in different directions from second starting point S2, and two regions, namely, third region143and fourth region144, may be identified as linearly extending in different directions from fourth starting point S4.

2-2. Function and Advantageous Effect

Next, a function and an advantageous effect of nitride semiconductor light-emitting element101according to the present embodiment will be described. The forward voltage in nitride semiconductor light-emitting element101according to the present embodiment will be described with reference toFIG.28.FIG.28is a graph indicating the relationship between forward voltage Vf and ratio r/a. Ratio r/a is the ratio of distance r from each of the corner portions to n-side contact region140to length a of the shorter side of nitride semiconductor light-emitting element101according to the present embodiment. The horizontal axis of the graph inFIG.28indicates ratio r/a and the vertical axis indicates forward voltage Vf.

In the graph illustrated inFIG.28, the experimental results of forward voltage Vf when distances r1, r2, r3, and r4are equal and proportion b of the area of n-side contact region140to the area of semiconductor stack structure1sin the plan view of main surface11aof substrate11is 0.2 are indicated. In this experiment, ratio r/a, etc. were varied under the condition that the area of the n-side contact region is equal. Distance r from each of the corner portions to n-side contact region40corresponds to distances r1, r2, r3and r4. Forward voltage Vf represents the forward voltage when the supply current is 1 A for nitride semiconductor light-emitting element101in which the shorter side and the longer side are the same 1 mm.

As illustrated inFIG.28, forward voltage Vf is a minimal value of approximately 3.4 V when ratio r/a is approximately 0.18, and is close to a minimum value of less than 3.8 V when ratio r/a is greater than 0 and less than or equal to 0.26.

Here, the advantageous effect of nitride semiconductor light-emitting element101according to the present embodiment will be described with comparison to nitride semiconductor light-emitting element1according to Embodiment 1. According to Embodiment 1, as indicated in graph (b) ofFIG.8, the distance from the vicinity of the center of each side of the peripheral edge of nitride semiconductor light-emitting element1to n-side contact region40is largest in p-side contact region60in the plan view of the main surface of the substrate. According to the present embodiment, first region141linearly extends from first starting point S1to second starting point S2, and thus it is possible to reduce the distance from (i) the vicinity of the center of the side of semiconductor stack structure1sincluding first corner portion C1and second corner portion C2in the p-side contact region to (ii) n-side contact region140. Accordingly, it is possible to reduce the electrical resistance of nitride semiconductor light-emitting element101in the same manner as Embodiment 1. As a result, it is possible to reduce the forward voltage in nitride semiconductor light-emitting element101according to the present embodiment.

Next, the relationship between forward voltage Vf and proportion b of the area of n-side contact region140to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element101according to the the present embodiment will be described with reference toFIG.29.FIG.29is a graph indicating the relationship between normalized forward voltage Vf and ratio r/a. Ratio r/a is the ratio of distance r from each of the corner portions to n-side contact region140to length a of the shorter side of nitride semiconductor light-emitting element101according to the present embodiment. The horizontal axis of the graph inFIG.29indicates ratio r/a and the vertical axis indicates normalized forward voltage Vf. InFIG.29, the experimental results when proportion b is 0.1, 0.2, and 0.3 are indicated by a triangle, a square, and a circle, respectively. Normalized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf of the case where ratio r/a is 0.

As illustrated inFIG.29, normalized forward voltage Vf has a minimal value in the range in which ratio r/a is greater than 0 and less than or equal to 0.26 for each of the cases where proportion b is 0.1, 0.2, and 0.3.

The maximum value of the ratio r/a indicated inFIG.29is ratio r/a when the gap inside n-side contact region140is eliminated as a result of n-side contact region140being away from the corner portion, and n-side contact region140no longer has an annular shape.

Here, the range of ratio r/a which allows normalized forward voltage Vf as indicated inFIG.29to be less than or equal to 1 will be considered. As illustrated inFIG.29, normalized forward voltage Vf is 1 when ratio r/a is 0, and normalized forward voltage Vf is less than or equal to 1 in the range in which ratio r/a is greater than 0 and less than or equal to a predetermined value. As indicated inFIG.29, the maximum value of the range of ratio r/a in which the normalized forward voltage Vf is less than or equal to 1 is greater than 0.26 for any proportion b. Accordingly, when proportion b is less than or equal to 0.3 and ratio r/a is less than or equal to 0.26, forward voltage Vf of nitride semiconductor light-emitting element101can be less than forward voltage Vf of the case where ratio r/a is 0.

Next, the range of ratio r/a which allows normalized forward voltage Vf as indicated inFIG.29to be smaller than in the case where ratio r/a is 0.26 will be considered. As illustrated inFIG.29, in the range in which ratio r/a is less than 0.26 and greater than or equal to a predetermined value, the normalized forward voltage can be smaller than in the case where ratio r/a is 0.26. For example, as indicated by the arrow inFIG.29, when proportion b is 0.1, the normalized forward voltage can be smaller than in the case where ratio r/a is 0.26 in the range in which ratio r/a is greater than or equal to approximately 0.12. Here, the minimum value of the range of ratio r/a which allows normalized forward voltage Vf to be smaller than in the case where ratio r/a is 0.26 will be described with reference toFIG.30.

FIG.30is a graph illustrating the relationship between proportion b and the minimum value of the range of ratio r/a that allows normalized forward voltage Vf to be smaller than in the case where ratio r/a is 0.26. Proportion b is the proportion of the area of n-side contact region140to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element101according to the present embodiment. The horizontal axis of the graph inFIG.30indicates proportion b, and the vertical axis indicates ratio r/a. InFIG.30, the minimum value of the range of ratio r/a is indicated by a square. It should be noted that ratio r/a in the case where normalized forward voltage Vf has a minimal value is also indicated by a triangle inFIG.30.

As illustrated inFIG.30, when the relationship between proportion b and the minimum value of the range of ratio r/a is approximated by a linear function of proportion b, the relationship can be represented by the following expression (21) when b is less than or equal to 0.3.

Accordingly, distances r1to r4, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (22) to (24).

This allows forward voltage Vf of nitride semiconductor light-emitting element101to be less than forward voltage Vf of the case where ratio r/a is 0.26.

Next, the relationship between a light emission output and proportion b of the area of n-side contact region140to the area of semiconductor stack structure1sof nitride semiconductor light-emitting element101will be described with reference toFIG.31.FIG.31is a graph indicating the relationship between (i) proportion b of the area of the n-side contact region to the area of the semiconductor stack structure of nitride semiconductor light-emitting element101according to the present embodiment and (ii) the ratio of the light emission output of nitride semiconductor light-emitting element101according to the present embodiment in the case where ratio r/a is the ratio when normalized forward voltage Vf has a minimal value to the light emission output of the nitride semiconductor light-emitting element according to the comparison example.FIG.31is a graph indicating the experimental results. The horizontal axis of the graph indicates proportion b and the vertical axis indicates the ratio of the light emission output. It should be noted that the nitride semiconductor light-emitting element according to the comparison example has the same configuration as the nitride semiconductor light-emitting element according to the comparison example described in Embodiment 1.

As illustrated inFIG.31, the ratio of the light emission output is greater than 1 in the entire range in which proportion b is less than or equal to 0.3. In other words, nitride semiconductor light-emitting element101according to the present embodiment has a greater light emission output than the nitride semiconductor light-emitting element according to the comparison example. In addition, as proportion b decreases from 0.3 to 0.07, the ratio of the light emission output increases substantially linearly, and as proportion b decreases further from 0.07, the ratio of the light emission output increases more steeply than linearly. Accordingly, in nitride semiconductor light-emitting element101according to the present embodiment, proportion b may satisfy b≤0.07. In this manner, it is possible to further increase the light emission output of nitride semiconductor light-emitting element101compared to the light emission output of the nitride semiconductor light-emitting element of the comparison example.

Next, a nitride semiconductor light-emitting element according to Variation 1 of Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present variation differs from nitride semiconductor light-emitting element101according to Embodiment 2 in that the n-side contact region includes 3 regions, etc. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element101according to Embodiment 2, with reference toFIG.32.

FIG.32is a plan view schematically illustrating the configuration of n-side contact region140aof nitride semiconductor light-emitting element101aaccording to the present variation.FIG.32illustrates n-side contact region140ain a plan view of main surface11aof substrate11.

As illustrated inFIG.32, n-side contact region140aaccording to the present variation includes first region141a, second region142a, and third region143a. First region141ais a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region142ais a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region143ais a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3.

According to the present variation, first region141alinearly extends from first starting point S1to third starting point S3. According to this configuration, first region141aand third region143aare connected to each other. Second region142alinearly extends from second starting point S2to first starting point S1. According to this configuration, second region142aand first region141aare connected to each other. Third region143alinearly extends from third starting point S3to fourth starting point S4. It should be noted that, in n-side contact region140aaccording to the present variation, first region141amay be identified as linearly extending from third starting point S3to first starting point S1. Second region142amay be identified as linearly extending from first starting point S1to second starting point S2. Third region143amay be identified as linearly extending from fourth starting point S4to third starting point S3. Furthermore, two regions, namely, first region141aand second region142a, may be identified as linearly extending in different directions from first starting point S1, and two regions, namely, first region141aand third region143a, may be identified as linearly extending in different directions from third starting point S3.

Distance r1between first corner portion C1and first starting point S1, distance r2between second corner portion C2and second starting point S2, distance r3between third corner portion C3and third starting point S3, and distance r4between fourth corner portion C4and fourth starting point S4are each less than or equal to 0.26 times length a of the shorter side of semiconductor stack structure1sin the plan view of main surface11aof substrate11. It should be noted that distances r1, r2, r3, and r4are not particularly limited as long as distances r1, r2, r3, and r4are each less than or equal to 0.26 times length a of the shorter side. According to the present variation, distances r1, r2, r3, and r4are equal to one another.

With nitride semiconductor light-emitting element101aaccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element101according to Embodiment 2 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 2 of Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element101according to Embodiment 2 in points other than that the n-side contact region includes n-side contact region40according to Embodiment 1 in addition to n-side contact region140according to Embodiment 2. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element101according to Embodiment 2, with reference toFIG.33.

FIG.33is a plan view illustrating the configuration of n-side contact region140bof nitride semiconductor light-emitting element101baccording to the present variation. It should be noted that the following describes the configurations of n-side contact region140b, etc. in a plan view of main surface11aof substrate11.

N-side contact region140bincludes first region141, second region142, third region143, and fourth region144, as with n-side contact region140according to Embodiment 2. N-side contact region140baccording to the present variation further includes first region41and second region42which are equivalent to those included in n-side contact region40according to Embodiment 1. First region41and second region42included in n-side contact region140baccording to the present variation are examples of a first additional region having a linear shape and extending from first starting point S1in a direction different from a direction of first region141and a second additional region having a linear shape and extending from second starting point S2in a direction different from a direction of second region142, respectively.

It should be noted that first region41may be identified as including: the first additional region having a linear shape and extending from first starting point S1in a direction different from a direction of first region141; and the third additional region having a linear shape and extending from third starting point S3in a direction different from a direction of third region143. In addition, second region42may be identified as including: the second additional region having a linear shape and extending from second starting point S2in a direction different from a direction of second region142; and the fourth additional region having a linear shape and extending from fourth starting point S4in a direction different from a direction of fourth region144. In this case, first region141and the second additional region are connected at second starting point S2, second region142and the third additional region are connected at third starting point S3, third region143and the fourth additional region are connected at fourth starting point S4, and fourth region144and the first additional region are connected at first starting point S1.

With nitride semiconductor light-emitting element101baccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element101according to Embodiment 2 are yielded as well.

Next, a nitride semiconductor light-emitting element according to Variation 3 of Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present variation matches nitride semiconductor light-emitting element101according to Embodiment 2 in points other than that the n-side contact region has four regions which are spaced apart from one another. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element101according to Embodiment 2.

First, the configuration of the n-side contact region according to the present variation will be described with reference toFIG.34.FIG.34is a plan view schematically illustrating the configuration of n-side contact region140cof nitride semiconductor light-emitting element101caccording to the present variation.FIG.34illustrates n-side contact region140cin a plan view of main surface11aof substrate11

As illustrated inFIG.34, n-side contact region140caccording to the present variation includes first region141c, second region142c, third region143c, and fourth region144c. First region141cis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region142cis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region143cis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region144cis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

According to the present variation, first region141clinearly extends from first starting point S1to a predetermined point located between first starting point S1and second starting point S2. Second region142cis disposed on the extended line of first region141cand spaced apart from first region141c. Second region142clinearly extends from second starting point S2to a predetermined point located between second starting point S2and third starting point S3. Third region143cis disposed on the extended line of second region142cand spaced apart from second region142c. Third region143clinearly extends from third starting point S3to a predetermined point located between third starting point S3and fourth starting point S4. Fourth region144cis disposed on the extended line of third region143cand spaced apart from third region143c. Fourth region144clinearly extends from fourth starting point S4to a predetermined point located between fourth starting point S4and first starting point S1. First region141cis disposed on the extended line of fourth region144cand spaced apart from fourth region144c.

As described above, first region141c, second region142c, third region143c, and fourth region144care spaced apart from each other. According to the present variation, first region141cis spaced apart from second starting point S2by distance d. In the same manner as first region141c, second region142c, third region143c, and fourth region144care also spaced apart from third starting point S3, fourth starting point S4, and first starting point S1, respectively, by distance d. It should be noted that, according to the present variation, distance d by which the regions are spaced apart from one another is constant. However, distance d need not necessarily be constant.

With nitride semiconductor light-emitting element101caccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element101according to Embodiment 2 are yielded as well.

Next, the relationship between forward voltage Vf and distance d by which the regions of n-side contact region140cof nitride semiconductor light-emitting element101caccording to the present variation are spaced apart from one another will be described with reference toFIG.35. It should be noted that, in the following description, the experimental results in the case where: r1=r2=r3=r4; and ratio r1/a is the ratio when normalized forward voltage Vf has a minimal value (indicated by the triangle inFIG.30) will be described.FIG.35is a graph indicating the relationship between normalized forward voltage Vf and ratio d/a. Ratio d/a is the ratio of distance d by which the regions are spaced apart from one another to length a of the shorter side of semiconductor stack structure1sof nitride semiconductor light-emitting element101caccording to the present variation. It should be noted that the horizontal axis of the graph inFIG.35indicates ratio d/a and the vertical axis indicates normalized forward voltage Vf. InFIG.35, the experimental results when proportion b of the area of n-side contact region140cto the area of semiconductor stack structure1sis 0.1, 0.2, and 0.3 are indicated by a circle, a square, and a triangle, respectively. Normalized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf of the case where ratio d/a is 0. In this experiment, ratio d/a, etc. were varied under the condition that the area of the n-side contact region is equal.

As indicated schematically in the graph ofFIG.35, as ratio d/a on the horizontal axis decreases, each region of n-side contact region140cbecomes narrower and longer, and as ratio d/a increases, each region of n-side contact region140cbecomes wider and shorter.

Here, the range of ratio d/a which allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum (i.e., the maximum value for the width of each region to be placeable) will be considered. For example, as illustrated inFIG.35, when proportion b is 0.3, the maximum value of ratio d/a is approximately 0.38, and normalized forward voltage Vf can be smaller than in the case where ratio d/a is at the maximum, in the range where ratio d/a is greater than or equal to approximately 0.33 and less than approximately 0.38. In the same manner, when proportion b is 0.1 and 0.2, the minimum value and the maximum value of the range of ratio d/a that allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum can also be obtained. The minimum value and the maximum value of the range of ratio d/a obtained as described above will be described with reference toFIG.36.FIG.36is a graph indicating the relationship between proportion b and the minimum and maximum values of ratio d/a of nitride semiconductor light-emitting element101caccording to the present variation. Proportion b is the proportion of the area of n-side contact region140cto the area of semiconductor stack structure1s. Ratio d/a is the ratio of distance d by which the regions are spaced apart from one another to length a of the shorter side of semiconductor stack structure1s. InFIG.36, the minimum value and the maximum value of the range of ratio d/a are indicated by a square and a diamond, respectively.

As illustrated inFIG.36, when the relationship between proportion b and the minimum value of ratio d/a is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (25) when b is greater than or equal to 0.1 and less than or equal to 0.3.

In addition, when the relationship between proportion b and the maximum value of ratio d/a is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (26) when b is greater than or equal to 0.1 and less than or equal to 0.3.

Accordingly, distance d, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (27) to (28).

This allows forward voltage Vf of nitride semiconductor light-emitting element101cto be less than forward voltage Vf of the case where ratio d/a is at the maximum.

Next, the range of ratio d/a which allows normalized forward voltage Vf as indicated inFIG.35to be less than or equal to 1 will be considered. As illustrated inFIG.35, normalized forward voltage Vf is 1 when ratio d/a is 0, and normalized forward voltage Vf is less than or equal to 1 in the range where ratio d/a is greater than 0 and less than or equal to a predetermined value. Here, the maximum value of the range of ratio d/a in which the normalized forward voltage Vf is less than or equal to 1 will be explained with reference toFIG.37.

FIG.37is a graph indicating the relationship between proportion b of the area of n-side contact region140cto the area of semiconductor stack structure1sof nitride semiconductor light-emitting element101caccording to the present variation and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1. The horizontal axis of the graph inFIG.37indicates proportion b, and the vertical axis indicates ratio d/a. InFIG.37, the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is indicated by a diamond.

As illustrated inFIG.37, when the relationship between proportion b and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (29) when b is greater than or equal to 0.1 and less than or equal to 0.3.

Accordingly, distance d, length a of the shorter side of semiconductor stack structure1sand proportion b may satisfy the following expressions (30) and (31).

This allows forward voltage Vf of nitride semiconductor light-emitting element101cto be less than forward voltage Vf of the case where ratio d/a is 0.

Next, a nitride semiconductor light-emitting element according to Variation 4 of Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present variation differs from nitride semiconductor light-emitting element101according to Embodiment 2 in that the n-side contact region includes 8 regions, etc. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element101according to Embodiment 2.

First, the configuration of the n-side contact region according to the present variation will be described with reference toFIG.38.FIG.38is a plan view schematically illustrating the configuration of n-side contact region140dof nitride semiconductor light-emitting element101daccording to the present variation.FIG.38illustrates n-side contact region140din a plan view of main surface11aof substrate11.

As illustrated inFIG.38, n-side contact region140daccording to the present variation includes first region141d, second region142d, third region143d, fourth region144d, first additional region151d, second additional region152d, third additional region153d, and fourth additional region154d.

First region141dis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region142dis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region143dis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region144dis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

First additional region151dis a linear region extending from first starting point S1in a direction different from first a direction of region141d. Second additional region152dis a linear region extending from second starting point S2in a direction different from a direction of second region142d. Third additional region153dis a linear region extending from third starting point S3in a direction different from a direction of third region143d. Fourth additional region154dis a linear region extending from fourth starting point S4in a direction different from a direction of fourth region144d.

Second additional region152dis disposed on the extended line of first region141dand spaced apart from first region141d, and extends in the same direction as first region141d. Third additional region153dis disposed on the extended line of second region142dand spaced apart from second region142d, and extends in the same direction as second region142d. Fourth additional region154dis disposed on the extended line of third region143dand spaced apart from third region143d, and extends in the same direction as third region143d. First additional region151dis disposed on the extended line of fourth region144dand spaced apart from fourth region144d, and extends in the same direction as fourth region144d.

As illustrated inFIG.38, distance d7between first region141dand second additional region152d, distance d8between second region142dand third additional region153d, distance d9between third region143dand fourth additional region154d, and distance d10between fourth region144dand first additional region151dare not particularly limited. According to the present embodiment, distances d7to d10are equal. In addition, the lengths of first region141d, second region142d, third region143d, fourth region144d, first additional region151d, second additional region152d, third additional region153d, and fourth additional region154dare equal to one another.

It should be noted that second additional region152dmay be identified as one example of the second region. In this case, the second region is disposed on the extended line of first region141dand spaced apart from first region141d, and extends in the same direction as first region141d.

With nitride semiconductor light-emitting element101daccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element101according to Embodiment 2 are yielded as well.

Next, the relationship between forward voltage Vf and distances d7to d10by which the regions of n-side contact region140dof nitride semiconductor light-emitting element101daccording to the present variation are spaced apart will be described with reference toFIG.39. It should be noted that, in the following description, the experimental results in the case where: d7=d8=d9=d10; r1=r2=r3=r4; and ratio r1/a is the ratio when normalized forward voltage Vf has a minimal value (indicated by a triangle inFIG.30) will be described.FIG.39is a graph indicating the relationship between forward voltage Vf and ratio d/a. Ratio d/a is the ratio of distance d by which the regions are spaced apart to length a of the shorter side of semiconductor stack structure1sof nitride semiconductor light-emitting element101daccording to the present variation. It should be noted that the horizontal axis of the graph inFIG.39indicates ratio d/a and the vertical axis indicates normalized forward voltage Vf. InFIG.39, the experimental results when proportion b of the area of n-side contact region140dto the area of semiconductor stack structure1sis 0.1, 0.2, and 0.3 are indicated by a circle, a square, and a triangle, respectively. Standardized forward voltage Vf represents the ratio of forward voltage Vf to forward voltage Vf when ratio d/a is 0. In this experiment, ratio d/a, etc. were varied under the condition that the area of the n-side contact region is equal.

As indicated schematically in the graph ofFIG.39, as ratio d/a on the horizontal axis becomes smaller, each region of n-side contact region140dbecomes narrower and longer, and as ratio d/a increases, each region of n-side contact region140dbecomes wider and shorter.

Here, the range of ratio d/a which allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum (i.e., the maximum value for the width of each region to be placeable) will be considered. For example, as illustrated inFIG.39, when proportion b is 0.3, the maximum value of ratio d/a is approximately 0.26, and normalized forward voltage Vf can be smaller than in the case where ratio d/a is at the maximum, in the range where ratio d/a is greater than or equal to approximately 0.15 and less than approximately 0.26. In the same manner, when proportion b is 0.1 and 0.2, the minimum value and the maximum value of the range of ratio d/a that allows normalized forward voltage Vf to be smaller than in the case where ratio d/a is at the maximum can also be obtained. The minimum value and the maximum value of the range of ratio d/a obtained in this manner will be described with reference toFIG.40.FIG.40is a graph indicating the relationship between proportion b and the minimum and maximum values of ratio d/a of nitride semiconductor light-emitting element101daccording to the present variation. Proportion b is the proportion of the area of n-side contact region140dto the area of semiconductor stack structure1s. Ratio d/a is the ratio of distance d by which the regions are spaced apart to length a of the shorter side of semiconductor stack structure1s. InFIG.40, the minimum value and the maximum value of the range of ratio d/a are indicated by a circle and a diamond, respectively.

As illustrated inFIG.40, when the relationship between proportion b and the minimum value of ratio d/a is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (32) when b is greater than or equal to 0.1 and less than or equal to 0.3. d/a=−2.5b2+1.75b−0.15 (32)

In addition, when the relationship between proportion b and the maximum value of ratio d/a is approximated by a linear function of proportion b, the relationship can be represented by the following expression (33) when b is less than or equal to 0.3.

Accordingly, distances d7to d10, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (34) to (36).

This allows forward voltage Vf of nitride semiconductor light-emitting element101dto be less than forward voltage Vf of the case where ratio d/a is at the maximum.

Next, the range of ratio d/a which allows normalized forward voltage Vf as indicated inFIG.39to be less than or equal to 1 will be considered. As illustrated inFIG.39, normalized forward voltage Vf is 1 when ratio d/a is 0, and normalized forward voltage Vf is less than or equal to 1 in the range where ratio d/a is greater than 0 and less than or equal to a predetermined value. Here, the maximum value of the range of ratio d/a in which the normalized forward voltage Vf is less than or equal to 1 will be explained with reference toFIG.41.

FIG.41is a graph indicating the relationship between proportion b of the area of n-side contact region140dto the area of semiconductor stack structure1sof nitride semiconductor light-emitting element101daccording to the present variation and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1. The horizontal axis of the graph inFIG.41indicates proportion b, and the vertical axis indicates ratio d/a. InFIG.41, the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is indicated by a diamond.

As illustrated inFIG.41, when the relationship between proportion b and the maximum value of ratio d/a which allows normalized forward voltage Vf to be less than or equal to 1 is approximated by a quadratic function of proportion b, the relationship can be represented by the following expression (37) when b is less than or equal to 0.3.

Accordingly, distances d7to d10, length a of the shorter side of semiconductor stack structure1s, and proportion b may satisfy the following expressions (38) to (40).

This allows forward voltage Vf of nitride semiconductor light-emitting element101dto be less than forward voltage Vf of the case where ratio d/a is 0.

Next, a nitride semiconductor light-emitting element according to Variation 5 of Embodiment 2 will be described. The nitride semiconductor light-emitting element according to the present variation differs from nitride semiconductor light-emitting element101according to Embodiment 2 in that the n-side contact region includes 8 regions, and that the regions extend in directions different from one another, etc. The following describes the nitride semiconductor light-emitting element according to the present variation focusing on the differences from nitride semiconductor light-emitting element101according to Embodiment 2, with reference toFIG.42.

FIG.42is a plan view schematically illustrating the configuration of n-side contact region140eof nitride semiconductor light-emitting element101eaccording to the present variation.FIG.42illustrates n-side contact region140ein a plan view of main surface11aof substrate11.

As illustrated inFIG.42, n-side contact region140eaccording to the present variation includes first region141e, second region142e, third region143e, fourth region144e, first additional region151e, second additional region152e, third additional region153e, and fourth additional region154e.

First region141eis a linear region extending in one direction from first starting point S1which is spaced apart from first corner portion C1. Second region142eis a linear region extending in one direction from second starting point S2which is spaced apart from second corner portion C2. Third region143eis a linear region extending in one direction from third starting point S3which is spaced apart from third corner portion C3. Fourth region144eis a linear region extending in one direction from fourth starting point S4which is spaced apart from fourth corner portion C4.

First additional region151eis a linear region extending from first starting point S1in a direction different from a direction of first region141e. Second additional region152eis a linear region extending from second starting point S2in a direction different from a direction of second region142e. Third additional region153eis a linear region extending from third starting point S3in a direction different from a direction of third region143e. Fourth additional region154eis a linear region extending from fourth starting point S4in a direction different from a direction of fourth region144e.

First region141eand second additional region152eare connected to each other, second region142eand third additional region153eare connected to each other, third region143eand fourth additional region154eare connected to each other, and fourth region144eand first additional region151eare connected to each other.

According to the present variation, second additional region152eextends in a direction different from a direction of first region141e. Third additional region153eextends in a direction different from a direction of second region142e. Fourth additional region154eextends in a direction different from a direction of third region143e. First additional region151eextends in a direction different from a direction of fourth region144e.

It should be noted that first region141eand second additional region152emay extend in the same direction, second region142eand third additional region153emay extend in the same direction, third region143eand fourth additional region154emay extend in the same direction, and fourth region144eand first additional region151emay extend in the same direction. In this case, nitride semiconductor light-emitting element101eaccording to the present variation has the same configuration as nitride semiconductor light-emitting element101according to Embodiment 2.

In nitride semiconductor light-emitting element101eaccording to the present variation that has the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element101according to Embodiment 2 are yielded as well.

A nitride semiconductor light-emitting element according to Embodiment 3 will be described. The nitride semiconductor light-emitting element according to the present embodiment differs mainly from the nitride semiconductor light-emitting element of Embodiment 1 in that the nitride semiconductor light-emitting element according to the present embodiment includes a plurality of n-side contact regions arranged in a matrix. The following describes the nitride semiconductor light-emitting element according to the present embodiment focusing on the differences from nitride semiconductor light-emitting element1according to Embodiment 1, with reference toFIG.43andFIG.44.

FIG.43is a plan view schematically illustrating the configuration of the plurality of n-side contact regions of nitride semiconductor light-emitting element201according to the present embodiment.FIG.43illustrates a plan view of main surface11aof substrate11in a plan view.

As illustrated inFIG.43, in nitride semiconductor light-emitting element201according to the present embodiment, in the plan view of main surface11aof substrate11, semiconductor stack structure1shas a rectangular shape, and includes first corner portion C1, second corner portion C2, third corner portion C3, and fourth corner portion C4. Second corner portion C2is a corner portion disposed on the same side of the rectangular outer edge of semiconductor stack structure1sas first corner portion C1. Third corner portion C3is a corner portion disposed diagonally to first corner portion C1on the rectangular outer edge of semiconductor stack structure1s. Fourth corner portion C4is a corner portion disposed diagonally to second corner portion C2the rectangular outer edge of semiconductor stack structure1s.

Nitride semiconductor light-emitting element201includes a plurality of n-side contact regions arranged in a matrix of at least three rows and three columns. According to the present embodiment, nitride semiconductor light-emitting element201includes nine n-side contact regions arranged in a matrix of three rows and three columns, namely,2411to2413,2421to2423, and2431to2433. Each of the n-side contact regions consists of a single region, i.e., a region that is continuously formed without separation. It should be noted that nitride semiconductor light-emitting element201according to the present embodiment includes a plurality of n-side contact electrodes each of which corresponds to a corresponding one of the plurality of n-side contact regions.

Each of the n-side contact regions will be described in detail below.

First, n-side contact region2411will be described. The nine n-side contact regions according to the present embodiment includes: n-side contact region2411that is one example of a first n-side contact region disposed in closest proximity to first corner portion C1; n-side contact region2412that is one example of a first Xn-side contact region disposed adjacent to the first n-side contact region in the row direction (i.e., in the horizontal direction ofFIG.43); and n-side contact region2421that is one example of a first Yn-side contact region disposed adjacent to the first n-side contact region in the column direction (i.e., in the vertical direction ofFIG.43).

N-side contact region2411is disposed in unit U11that is one example of a first unit having a rectangular shape and enclosed by: straight line LC1that is equidistant from center of gravity G11of n-side contact region2411and center of gravity G12of n-side contact region2412; straight line LR1that is equidistant from center of gravity G11of n-side contact region2411and center of gravity G21of n-side contact region2421; and the outer edge of semiconductor stack structure1s.

N-side contact region2411includes first region2411ahaving a linear shape and extending in one direction from first starting point S111which is spaced apart from first corner portion C1. A p-side contact region is disposed between first starting point S111and first corner portion C1, and distance r1between first corner portion C1and first starting point S111is less than or equal to 0.26 times length a1 of the shorter side of unit U11.

Nitride semiconductor light-emitting element201includes first region2411aas described above, and thus it is possible to reduce the forward voltage in unit U11in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1. As a result, it is possible to reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

In addition, n-side contact region2411includes region2411bhaving a linear shape and extending in one direction from starting point S112which is spaced apart from the corner portion disposed on the same side of unit U11as first corner portion C1. Here, the corner portion disposed on the same side of unit U11as first corner portion C1is the intersection of the outer edge of semiconductor stack structure1sand straight line LR1. P-side contact region60is disposed between starting point S112and the intersection of the outer edge of semiconductor stack structure is and straight line LR1, and the distance between starting point S112and the intersection of the outer edge of semiconductor stack structure1sand straight line LR1is less than or equal to 0.26 times length a1 of the shorter side of unit U11.

Nitride semiconductor light-emitting element201includes region2411bas described above, and thus it is possible to further reduce the forward voltage in unit U11.

Next, n-side contact regions2431,2433, and2413will be described. The nine n-side contact regions include: n-side contact region2431that is one example of a second n-side contact region disposed in closest proximity to second corner portion C2; n-side contact region2432that is one example of a second Xn-side contact region disposed adjacent to the second n-side contact region in the row direction; and a second Yn-side contact region disposed adjacent to the second n-side contact region in the column direction.

In addition, the nine n-side contact regions include: n-side contact region2433that is one example of a third n-side contact region disposed in closest proximity to third corner portion C3; n-side contact region2432that is one example of a third Xn-side contact region disposed adjacent to the third n-side contact region in the row direction; and n-side contact region2423that is one example of a third Yn-side contact region disposed adjacent to the third n-side contact region in the column direction.

In addition, the nine n-side contact regions include: n-side contact region2413that is one example of a fourth n-side contact region disposed in closest proximity to fourth corner portion C4; n-side contact region2412that is one example of a fourth Xn-side contact region disposed adjacent to the fourth n-side contact region in the row direction; and n-side contact region2423that is one example of a fourth Yn-side contact region disposed adjacent to the fourth n-side contact region in the column direction.

N-side contact region2431is disposed in unit U31that is one example of a second unit having a rectangular shape and enclosed by: straight line LC1that is equidistant from center of gravity G31of n-side contact region2431and center of gravity G32of n-side contact region2432; straight line LR2that is equidistant from center of gravity G31of n-side contact region2431and center of gravity G21of n-side contact region2421; and the outer edge of semiconductor stack structure1s. It should be noted that, according to the present embodiment, the straight line equidistant from center of gravity G11and center of gravity G12and the straight line equidistant from center of gravity G31and center of gravity G32are the same straight line LC1.

N-side contact region2433is disposed in unit U33that is one example of a third unit having a rectangular shape and enclosed by: straight line LC2that is equidistant from center of gravity G33of n-side contact region2433and center of gravity G32of n-side contact region2432; straight line LR2that is equidistant from center of gravity G33of n-side contact region2433and center of gravity G23of n-side contact region2423; and the outer edge of semiconductor stack structure1s. It should be noted that, according to the present embodiment, the straight line equidistant from center of gravity G21and center of gravity G31and the straight line equidistant from center of gravity G23and center of gravity G33are the same straight line LR2.

N-side contact region2413is disposed in unit U13that is one example of a fourth unit having a rectangular shape and enclosed by: straight line LC2that is equidistant from center of gravity G13of n-side contact region2413and center of gravity G12of n-side contact region2412; straight line LR1that is equidistant from center of gravity G13of n-side contact region2413and center of gravity G23of n-side contact region2423; and the outer edge of semiconductor stack structure1s. It should be noted that, according to the present embodiment, the straight line equidistant from center of gravity G33and center of gravity G32and the straight line equidistant from center of gravity G13and center of gravity G12are the same straight line LC2. It should be noted that, according to the present embodiment, the straight line equidistant from center of gravity G11and center of gravity G21and the straight line equidistant from center of gravity G13and center of gravity G23are the same straight line LR1.

N-side contact region2431includes second region2431ahaving a linear shape and extending in one direction from second starting point S311which is spaced apart from second corner portion C2. N-side contact region2433includes third region2433ahaving a linear shape and extending in one direction from third starting point S331which is spaced apart from third corner portion C3. N-side contact region2413includes fourth region2413ahaving a linear shape and extending in one direction from fourth starting point S131which is spaced apart from fourth corner portion C4.

P-side contact region60is disposed between second starting point S311and second corner portion C2, between third starting point S331and third corner portion C3, and between fourth starting point S131and fourth corner portion C4.

Distance r2between second corner portion C2and second starting point S311is less than or equal to 0.26 times length a2 of the shorter side of unit U31, distance r3between third corner portion C3and third starting point S331is less than or equal to 0.26 times length a3 of the shorter side of unit U33, distance r4between fourth corner portion C4and fourth starting point S131is less than or equal to 0.26 times length a4 of the shorter side of the fourth unit.

Nitride semiconductor light-emitting element201includes second region2431a, third region2433a, and fourth region2413aas described above, and thus it is possible to reduce the forward voltage in units U31, U33, and U13in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1. As a result, it is possible to reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

N-side contact region2431includes region2431bhaving a linear shape and extending in one direction from starting point S312which is spaced apart from the corner portion disposed on the same side of unit U31as second corner portion C2. Here, the corner portion disposed on the same side of unit U31as second corner portion C2is the intersection of the outer edge of semiconductor stack structure1sand straight line LR2. P-side contact region60is disposed between starting point S312and the intersection of the outer edge of semiconductor stack structure1sand straight line LR2, and the distance between starting point S312and the intersection of the outer edge of semiconductor stack structure1sand straight line LR2is less than or equal to 0.26 times length a2 of the shorter side of unit U31.

N-side contact region2433includes region2433bhaving a linear shape and extending in one direction from starting point S332which is spaced apart from the corner portion disposed on the same side of unit U33as third corner portion C3. Here, the corner portion disposed on the same side of unit U33as third corner portion C3is the intersection of the outer edge of semiconductor stack structure1sand straight line LR2. P-side contact region60is disposed between starting point S332and the intersection of the outer edge of semiconductor stack structure1sand straight line LR2, and the distance between starting point S332and the intersection of the outer edge of semiconductor stack structure1sand straight line LR2is less than or equal to 0.26 times length a3 of the shorter side of unit U33.

N-side contact region2413includes region2413bhaving a linear shape and extending in one direction from starting point S132which is spaced apart from the corner portion disposed on the same side of unit U13as fourth corner portion C4. Here, the corner portion disposed on the same side of unit U13as fourth corner portion C4is the intersection of the outer edge of semiconductor stack structure1sand straight line LR1. P-side contact region60is disposed between starting point S132and the intersection of the outer edge of semiconductor stack structure1sand straight line LR1, and the distance between starting point S132and the intersection of the outer edge of semiconductor stack structure1sand straight line LR1is less than or equal to 0.26 times length a4 of the shorter side of unit U13.

Nitride semiconductor light-emitting element201includes regions2431b,2433b, and2413bas described above, and thus it is possible to further reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

According to the present embodiment, each of units U11, U31, U33, and U13has the same configuration as nitride semiconductor light-emitting element1according to Embodiment 1. In other words, in unit U11, (i) the distance from the intersection of straight line LR1and straight line LC1to first region2411aand (ii) the distance from the intersection of the outer edge of semiconductor stack structure1sand straight line LC1to region2411bare each less than or equal to 0.26 times length a1 of the shorter side of unit U11. In unit U31, (i) the distance from the intersection of straight line LR2and straight line LC1to second region2431aand (ii) the distance from the intersection of the outer edge of semiconductor stack structure is and straight line LC1to region2431bare each less than or equal to 0.26 times length a2 of the shorter side of unit U31. In unit U33, (i) the distance from the intersection of straight line LR2and straight line LC2to third region2433aand (ii) the distance from the intersection of the outer edge of semiconductor stack structure1sand straight line LC2to region2433bare each less than or equal to 0.26 times length a3 of the shorter side of unit U33. In unit U13, (i) the distance from the intersection of straight line LR1and straight line LC2to fourth region2413aand (ii) the distance from the intersection of the outer edge of semiconductor stack structure1sand straight line LC2to region2413bare each less than or equal to 0.26 times length a4 of the shorter side of unit U13. In each of the units, the n-side contact region has an X shape as described above, and the proportion of the area of the n-side contact region to the area of the unit is less than or equal to 0.3. Accordingly, it is possible to reduce the forward voltage in the same manner as Embodiment 1. In addition, the proportion of the area of the nine n-side contact regions to the area of semiconductor stack structure1smay be less than or equal to 0.1. According to this configuration, it is possible to increase the light emission output of nitride semiconductor light-emitting element201in the same manner as Embodiment 1.

Next, unit U22that includes, among the nine n-side contact regions illustrated inFIG.43, n-side contact region2422positioned at the center of the matrix of three rows and three columns will be described with reference toFIG.44in addition toFIG.43. Unit U22is one example of a unit disposed in the i-th row (2≤i≤N−1) and the j-th column (2≤j≤M−1) in the plurality of n-side contact regions arranged in a matrix of N rows and M columns (N≥3, M≥3).FIG.44is a plan view schematically illustrating the configuration of unit U22including the n-side contact region locate at the center among the plurality of n-side contact regions according to the present embodiment.FIG.44illustrates only the portion of unit U22in detail out ofFIG.43.

As illustrated inFIG.43, according to the present embodiment, the nine n-side contact regions are arranged in a matrix of three rows and three columns. The centers of gravity of three n-side contact regions disposed in each of the first to third rows among the nine n-side contact regions are on a straight line. The centers of gravity of three n-side contact regions disposed in each of the first to third columns among the nine n-side contact regions are on a straight line.

As illustrated inFIG.43andFIG.44, unit U22is enclosed by straight line LR1, straight line LR2, straight line LC1, and straight line LC2.

Straight line GR1illustrated inFIG.43is a straight line connecting centers of gravity G11, G12, and G13of three n-side contact regions2411,2412, and2413, respectively, disposed in the first row. Straight line GR2is a straight line connecting centers of gravity G21, G22, and G23of three n-side contact regions2421,2422, and2423, respectively, disposed in the second row. Straight line LR1is a straight line that divides equally a region between straight line GR1and straight line GR2. Straight line GR3is a straight line connecting centers of gravity G31, G32, and G33of three n-side contact regions2431,2432, and2433, respectively, disposed in the third row. Straight line LR2is a straight line that divides equally a region between straight line GR2and straight line GR3. Straight line GC1is a straight line connecting centers of gravity G11, G21, and G31of three n-side contact regions2411,2421, and2431, respectively, disposed in the first column. Straight line GC2is a straight line connecting centers of gravity G12, G22, and G32of three n-side contact regions2412,2422, and2432, respectively, disposed in the second column, and straight line LC1is a straight line that divides equally a region between straight line GC1and straight line GC2. Straight line GC3is a straight line connecting centers of gravity G13, G23, and G33of three n-side contact regions2413,2423, and2433, respectively, disposed in the third column. Straight line LC2is a straight line that divides equally a region between straight line GC2and straight line GC3.

As illustrated inFIG.44, unit U22includes: first unit corner portion C221between straight line LR1and straight line LC1(i.e., the intersection of straight line LR1and straight line LC1); second unit corner portion C222between straight line LR2and straight line LC1(i.e., the intersection of straight line LR2and straight line LC1); third unit corner portion C223disposed diagonally to first unit corner portion C221(i.e., the intersection of straight line LR2and straight line LC2); and fourth unit corner portion C224disposed diagonally to second unit corner portion C222(i.e., the intersection of straight line LR1and straight line LC2).

N-side contact region2422disposed in unit U22includes first unit region2422ahaving a linear shape and extending in one direction from first unit starting point S221which is spaced apart from first unit corner portion C221, and p-side contact region60is disposed between first unit starting point S221and first unit corner portion C221. Distance ru1between first unit corner portion C221and first unit starting point S221is less than or equal to 0.26 times length au1 of the shorter side of unit U22.

Nitride semiconductor light-emitting element201includes first unit region2422aas described above, and thus it is possible to reduce the forward voltage in unit U22in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1. As a result, it is possible to reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

N-side contact region2422disposed in unit U22includes: second unit region2422bhaving a linear shape and extending in one direction from second unit starting point S222which is spaced apart from second unit corner portion C222; third unit region2422chaving a linear shape and extending in one direction from third unit starting point S223which is spaced apart from third unit corner portion C223; and fourth unit region2422dhaving a linear shape and extending in one direction from fourth unit starting point S224which is spaced apart from fourth unit corner portion C224.

First unit region2422ais connected to third unit region2422c, and second unit region2422bis connected to fourth unit region2422d. First unit region2422a, second unit region2422b, third unit region2422c, and fourth unit region2422dare connected at center of gravity G22of n-side contact region2422. First unit region2422aand third unit region2422cextend in the same direction, and second unit region2422band fourth unit region2422dextend in the same direction.

P-side contact region60is disposed between second unit starting point S222and second unit corner portion C222, between third unit starting point S223and third unit corner portion C223, and between fourth unit starting point S224and fourth unit corner portion C224.

Distance ru2between second unit corner portion C222and second unit starting point S222, distance ru3between third unit corner portion C223and third unit starting point S223, and distance ru4between fourth unit corner portion C224and fourth unit starting point S224are each less than or equal to 0.26 times length au1 of the shorter side of unit U22.

Nitride semiconductor light-emitting element201includes second unit region2422b, third unit region2422c, and fourth unit region2422das described above. In other words, unit U22has the same configuration as nitride semiconductor light-emitting element1according to Embodiment 1. Accordingly, with nitride semiconductor light-emitting element201, it is possible to further reduce the forward voltage in unit U22in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1. As a result, it is possible to further reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

As illustrated inFIG.43, n-side contact regions2412,2421,2423, and2432are disposed in units U12, U21, U23, and U32, respectively. Unit U12is a unit enclosed by the outer edge of semiconductor stack structure1s, straight line LR1, straight line LC1, and straight line LC2. Unit U21is a unit enclosed by straight line LR1, straight line LR2, the outer edge of semiconductor stack structure1s, and straight line LC1. Unit U23is a unit enclosed by straight line LR1, straight line LR2, straight line LC2, and the outer edge of semiconductor stack structure1s. Unit U32is a unit enclosed by straight line LR2, the outer edge of semiconductor stack structure1s, straight line LC1, and straight line LC2.

The configuration of each of the n-side contact regions is not particularly limited, but each of the n-side contact regions according to the present embodiment has an X shape as with the other n-side contact regions described above, and the distance from the corner portion of the unit to the n-side contact region is less than or equal to 0.26 times the length of the shorter side of the unit. Nitride semiconductor light-emitting element201includes units U12, U21, U23, and U32in which such n-side contact regions are disposed, and thus it is possible to further reduce the forward voltage in each of the units in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1. As a result, it is possible to further reduce the forward voltage in the entirety of nitride semiconductor light-emitting element201.

3-5. Other Configuration of N-Side Contact Region

In the present embodiment, nitride semiconductor light-emitting element201including nine n-side contact regions arranged in a matrix of three rows and three columns has been described, but the configuration of the plurality of n-side contact regions according to the present embodiment is not limited to this. The plurality of n-side contact regions may be arranged in a matrix of N rows and M columns (N≥3 and M≥3). Here, the centers of gravity of M n-side contact regions disposed in each of the first to N-th rows among the plurality of n-side contact regions are on a straight line. The centers of gravity of N n-side contact regions disposed in each of the first to M-th columns among the plurality of n-side contact regions are on a straight line.

In such a configuration as well, the n-side contact region disposed in the i-th row (2≤i≤N−1) and the j-th column (2≤j≤M−1) may have the following configuration in the same manner as n-side contact region2422described above.

The unit in which the n-side contact region disposed at the intersection of the i-th row and the j-th column is enclosed by third straight line L3, fifth straight line L5, eighth straight line L8, and tenth straight line L10in the same manner as unit U22illustrated inFIG.44. Here, as illustrated inFIG.44, straight line LR1, straight line LR2, straight line LC1, and straight line LC2of nitride semiconductor light-emitting element201are examples of third straight line L3, fifth straight line L5, eighth straight line L8, and tenth straight line L10, respectively.

Third straight line L3is a straight line that divides equally a region between first straight line L1and second straight line L2. First straight line L1connects the centers of gravity of M n-side contact regions disposed in the i−1-th row (2≤i≤N−1). Second straight line L2connects the centers of gravity of M n-side contact regions disposed in the i-th row. Here, as illustrated inFIG.43, straight line GR1and straight line GR2of nitride semiconductor light-emitting element201are examples of first straight line L1and second straight line L2, respectively.

Fifth straight line L5is a straight line that divides equally a region between second straight line L2and fourth straight line L4that connects the centers of gravity of M n-side contact regions disposed in the i+1-th row. Here, as illustrated inFIG.43, straight line GR3of nitride semiconductor light-emitting element201is one example of fourth straight line L4.

Eighth straight line L8is a straight line that divides equally a region between sixth straight line L6and seventh straight line L7. Sixth straight line connects the centers of gravity of N n-side contact regions disposed in the j−1-th column. Seventh straight line L7connects the centers of gravity of N n-side contact regions disposed in the j-th column. Here, as illustrated inFIG.43, straight line GC1and straight line GC2of nitride semiconductor light-emitting element201are examples of sixth straight line L6and seventh straight line L7, respectively.

Tenth straight line L10is a straight line that divides equally a region between seventh straight line L7and ninth straight line L9that connects the centers of gravity of N n-side contact regions disposed in the j+1-th column. Here, as illustrated inFIG.43, straight line GC3of nitride semiconductor light-emitting element201is one example of ninth straight line L9.

The unit in which the n-side contact region disposed at the intersection of i-th row and the j-th column includes: a first unit corner portion between third straight line L3and eighth straight line L8; a second unit corner portion between fifth straight line L5and eighth straight line L8; a third unit corner portion disposed diagonally to the first unit corner portion; and a fourth unit corner portion disposed diagonally to the second unit corner portion. Here, first unit corner portion C221, second unit corner portion C222, third unit corner portion C223, and fourth unit corner portion C224illustrated inFIG.44are examples of the first unit corner portion, the second unit corner portion, the third unit corner portion, and the fourth unit corner portion, respectively.

The n-side contact region disposed in the above-described unit includes first unit region having a linear shape and extending in one direction from the first unit starting point that is spaced apart from the first unit corner portion. Here, first unit region2422aillustrated inFIG.44is one example of the first unit region. P-side contact region60is disposed between the first unit starting point and the first unit corner portion. In addition, distance ru1between the first unit corner portion and the first unit starting point is less than or equal to 0.26 times length au1 of the shorter side of the unit.

Among the plurality of n-side contact regions, n-side contact regions disposed in all of the units that satisfy 2≤i≤N−1, and 2≤j≤M−1 may each include the first unit region as described above.

According to this configuration, among the plurality of n-side contact regions arranged in a matrix, all of the n-side contact regions other than those disposed in outer edge portions include the first unit regions as described above. Accordingly, it is possible to reduce the forward voltage in the units other than those disposed in the outer edge portions in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1.

The n-side contact region disposed in the above-described unit may include: a second unit region having a linear shape and extending in one direction from the second unit starting point that is spaced apart from the second unit corner portion; a third unit region having a linear shape and extending in one direction from the third unit starting point that is spaced apart from the third unit corner portion; and a fourth unit region having a linear shape and extending in one direction from the fourth unit starting point that is spaced apart from the fourth unit corner portion. Here, second unit region2422b, third unit region2422c; and fourth unit region2422dillustrated inFIG.44are examples of the second unit region, the third unit region, and the fourth unit region, respectively. P-side contact region60is disposed between the second unit starting point and the second unit corner portion, between the third unit starting point and the third unit corner portion, and between the fourth unit starting point and the fourth unit corner portion.

Distance ru2between the second unit corner portion and the second unit starting point, distance ru3between the third unit corner portion and the third unit starting point, and distance ru4between the fourth unit corner portion and the fourth unit starting point are each less than or equal to 0.26 times length au1 of the shorter side of the unit.

According to this configuration, among the plurality of n-side contact regions arranged in a matrix, all of the n-side contact regions other than those disposed in outer edge portions include the second to the fourth unit regions as described above. Accordingly, it is possible to further reduce the forward voltage in the units other than those disposed in the outer edge portions, in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1.

It should be noted that, according to the present embodiment, the n-side contact region disposed in each unit has the configuration equivalent to the configuration of n-side contact region40according to Embodiment 1, but the configuration of each of the n-side contact regions according to the present embodiment is not limited to this. For example, each of the n-side contact regions may have the configuration equivalent to the configuration of Embodiment 1, Embodiment 2, and the variations of Embodiment 1 and Embodiment 2 as described above. For example, each of the plurality of n-side contact regions included in the nitride semiconductor light-emitting element may have a rectangular annular shape as indicated in Embodiment 2 and the variations thereof. In this case, as with Embodiment 2, proportion b of the area of the n-side contact region to the area of the semiconductor stack structure may satisfy b≤0.07. In addition, the plurality of n-side contact regions included in the nitride semiconductor light-emitting element may all have the same configuration, or may respectively have different configurations. In addition, among the plurality of n-side contact regions, one or more of the n-side contact regions may have a configuration different from the n-side contact region according to present disclosure. For example, one or more of the n-side contact regions may have a configuration equivalent to the configuration of the n-side contact region of the comparison example described in Embodiment 1.

A nitride semiconductor light-emitting element according to Embodiment 4 will be described. The nitride semiconductor light-emitting element according to the present embodiment matches nitride semiconductor light-emitting element1according to Embodiment 1 in the configuration other than the configuration of the electrodes. The following describes the nitride semiconductor light-emitting element according to the present embodiment focusing on the differences from nitride semiconductor light-emitting element1according to Embodiment 1.

4-1. Overall Configuration

First, an overall configuration of the nitride semiconductor light-emitting element according to the present embodiment will be described with reference toFIG.45.FIG.45is a diagram schematically illustrating the overall configuration of nitride semiconductor light-emitting element301according to the present embodiment.FIG.45illustrates plan view (a) and cross-sectional view (b) of nitride semiconductor light-emitting element301. Cross-sectional view (b) ofFIG.45illustrates a cross-section surface taken along line45B-45B indicated in plan view (a).

As illustrated inFIG.45, nitride semiconductor light-emitting element301includes substrate11, semiconductor stack structure1s, p-side contact electrode16, insulating layer317, n-side electrode319, and cover electrode318. According to the present embodiment, nitride semiconductor light-emitting element301is a flip-chip LED in which semiconductor stack structure1s, n-side electrode319, and p-side contact electrode16are arranged on a main surface11aside of substrate11. Main surface11ais one of main surfaces of substrate11.

P-side contact electrode16includes the same configuration as the configuration of p-side contact electrode16according to Embodiment 1. According to the present embodiment, p-side contact electrode16is in contact with P-type semiconductor layer14in p-side contact region360. Insulating layer317and n-side electrode319are disposed above a portion of p-side contact electrode16.

Insulating layer317is a layer that comprises an insulating material that covers continuously a portion of exposure portion12ein which n-type semiconductor layer12is exposed and a portion above p-type semiconductor layer14. Insulating layer317may include an opening portion defined above exposure portion12e. Insulating layer317is also disposed in a region of a portion above p-side contact electrode16. According to the present embodiment, insulating layer317covers at least half the region above p-side contact electrode16. The configuration of insulating layer317is not particularly limited as long as insulating layer317is a layer that comprises an insulating material. According to the present embodiment, insulating layer317is a layer comprising SiO2and has a thickness of 1.0 μm.

N-side electrode319is one example of the n-side contact electrode that is disposed above n-type semiconductor layer12and is in contact with n-type semiconductor layer12in n-side contact region340. N-side electrode319is disposed on exposure portion12ein which n-type semiconductor layer12is exposed, and also disposed on a region of a portion above p-type semiconductor layer14. More specifically, as illustrated in cross-sectional view (b) ofFIG.45, n-side electrode319covers continuously the portion from exposure portion12eto a portion above p-type semiconductor layer14and p-side contact electrode16. Insulating layer317is disposed between n-side electrode319and p-side contact electrode16. According to this configuration, n-side electrode319and p-side contact electrode16are insulated. The configuration of n-side electrode319is not particularly limited as long as n-side electrode319is a conductive layer that makes ohmic contact with n-type semiconductor layer12. According to the present embodiment, n-side electrode319is a stack structure including an Al layer having a thickness of 0.3 μm, a Ti layer having a thickness of 0.3 μm, and an Au layer having a thickness of 1.0 μm, which are stacked in sequence from the n-type semiconductor layer12side.

Cover electrode318is an electrode that covers p-side contact electrode16. The configuration of cover electrode318is not particularly limited as long as cover electrode318is a conductive film. According to the present embodiment, cover electrode318is a stack structure including an Al layer having a thickness of 0.3 μm, a Ti layer having a thickness of 0.3 μm, and an Au layer having a thickness of 1.0 μm, which are stacked in sequence so as to cover a portion of p-side contact electrode16. It should be noted that cover electrode318may have the configuration equivalent to the configuration of n-side electrode319.

With nitride semiconductor light-emitting element301having the configuration as described above, the same advantageous effects as those of nitride semiconductor light-emitting element1according to Embodiment 1 are yielded as well.

Next, A mounting aspect of nitride semiconductor light-emitting element301according to the present embodiment will be described.FIG.46is a cross sectional view schematically illustrating one example of the mounting aspect of nitride semiconductor light-emitting element301according to the present embodiment.

As illustrated inFIG.46, in one example of the mounting aspect of nitride semiconductor light-emitting element301according to the present embodiment, nitride semiconductor light-emitting element301is flip-chip mounted on mounted board25in the same manner as nitride semiconductor light-emitting element1according to Embodiment 1.

Nitride semiconductor light-emitting element301is mounted on mounting substrate25as described above. With the configuration as described above, an electric current is supplied to nitride semiconductor light-emitting element301from the mounting substrate25side, and light generated in active layer13is emitted from the substrate11side of nitride semiconductor light-emitting element301.

4-3. Manufacturing Method

Next, the manufacturing method of nitride semiconductor light-emitting element301according to the present embodiment will be described with reference toFIG.47toFIG.50.FIG.47toFIG.50are cross sectional views schematically illustrating the processes of manufacturing nitride semiconductor light-emitting element301according to the present embodiment.

First, as illustrated inFIG.47, substrate11is prepared, and semiconductor stack structure1sis stacked on main surface11athat is one of the main surfaces of substrate11, in the same manner as the manufacturing method of nitride semiconductor light-emitting element1according to Embodiment 1.

Then, as illustrated inFIG.48, p-side contact electrode16having a predetermined shape is formed above p-type semiconductor layer14, in the same manner as the manufacturing method of nitride semiconductor light-emitting element1according to Embodiment 1.

Then, as illustrated inFIG.49, insulating layer317is formed. According to the present embodiment, an oxide film that comprises SiO2and has a thickness of 1.0 μm is deposited on the entire surface above semiconductor stack structure1sand p-side contact electrode16. Then, a resist pattern is formed in which portions of n-type semiconductor layer12and p-type semiconductor layer14are opened, and the resist is removed after the oxide film in the region in which the resist pattern is not formed is removed by wet etching. In this manner, insulating layer317in which the portions above exposure portion12eand above p-side contact electrode16of the oxide film are removed is formed.

Then, as illustrated inFIG.50, n-side electrode319having a predetermined shape is formed in the region in which insulating layer317is not disposed in exposure portion12e, and in a portion of the region in which insulating layer317is disposed above p-type semiconductor layer14. In addition, cover electrode318having a predetermined shape is formed in the region in which p-side contact electrode16is disposed above p-type semiconductor layer14. Cover electrode318may also be disposed above insulating layer317. N-side electrode319and cover electrode318may have an equivalent layer configuration and be concurrently formed. According to the present embodiment, a resist pattern is formed to cover the region between the region in which n-side electrode319is formed and the region in which cover electrode318is formed, and a stacked film including an Al film having a thickness of 0.3 μm, a Ti film having a thickness of 0.3 μm, and an Au film having a thickness of 1.0 μm is formed using an EB deposition method. Then, n-side electrode319including an Al layer, a Ti layer, and an Au layer and cover electrode318are formed by removing the resist and the stacked film above the resist by the lift-off method.

As described above, nitride semiconductor light-emitting element301according to the present embodiment can be manufactured.

The nitride semiconductor light-emitting element according to the present disclosure has been described above based on the embodiments and the variations, but the present disclosure is not limited to the above embodiments and the variations.

For example, although each of the n-side contact regions includes the second region and the like in addition to the first region, it is sufficient if each of the n-side contact regions includes at least the first region.

In addition, in each of the embodiments and variations described above, the configuration of the first region extending from the first starting point and the configuration of the first region and the first additional region extending from the first starting point have been described, but the configuration of the region extending from the first starting point is not limited to these configurations. For example, three or more regions each having a linear shape may extend from the first starting point. The same holds true for the regions extending from the second to fourth starting points.

In addition, as a nitride semiconductor light-emitting element according to each of the embodiments and variations described above, an element that emits light having a wavelength in the 450 nm band has been described, but the nitride semiconductor light-emitting element is not limited to this and may also emit light having a wavelength in other wavelength bands.

In addition, forms obtained by various modifications to the respective exemplary embodiments described above that can be conceived by a person of skill in the art as well as forms realized by arbitrarily combining structural components and functions in the respective exemplary embodiments described above which are within the scope of the essence of the present disclosure are also included in the present disclosure.

INDUSTRIAL APPLICABILITY

The nitride semiconductor light-emitting element according to the present disclosure is applicable as, for example, as a small high-power light source, automotive headlamp devices, etc.