Light emitting element

A light emitting element includes a semiconductor layer which is in a planar shape of a polygon at least of a pentagon, a second electrode provided on the semiconductor layer, and a first electrode provided on the semiconductor layer and having a first pad portion, a first extension portion that extends from the first pad portion along an imaginary circle to which the first pad portion is tangent on the inside and whose center is at the same location as center of gravity of the polygon shape, and a second extension portion that extends along the imaginary circle from the first pad portion on the opposite side from the first extension portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application Nos. 2015-36172 and 2015-236336 filed on Feb. 26, 2015 and Dec. 3, 2015. The entire disclosure of Japanese Patent Application Nos. 2015-36172 and 2015-236336 is hereby incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a light emitting element.

2. Description of Related Art

Many different light emitting elements have been developed in the past in an effort to make uniform light emission possible. For example, a light emitting element has been proposed in which the electrode structure of the light emitting element, whose planar shape is quadrangular, is such that either a first electrode or a second electrode is disposed on the top face of the light emitting element, and the other electrode is disposed surrounding the periphery of the one electrode (for example, JP2010-225771A, JP2002-319705A and WO2012/011458). With this electrode structure, a uniform distribution of current density is achieved, so that light is emitted uniformly over the entire top face of the light emitting element.

There is a need for a light emitting element that offers more uniform distribution of current density than the distribution of current density resulting from these various electrode structures, and that emits more uniform light over the entire top face of the light emitting element.

SUMMARY

A light emitting device of the present disclosure includes a semiconductor layer which is in a planar shape of a polygon at least of a pentagon, a second electrode provided on the semiconductor layer, and a first electrode provided on the semiconductor layer. The first electrode has a first pad portion, a first extension portion that extends from the first pad portion along an imaginary circle to which the first pad portion is tangent on the inside and whose center is at the same location as center of gravity of the polygon shape and, a second extension portion that extends along the imaginary circle from the first pad portion on the opposite side from the first extension portion.

Another light emitting device of the present disclosure includes a semiconductor layer which is in a planar shape of a polygon at least of a pentagon, a second electrode provided on the semiconductor layer, and a first electrode provided on the semiconductor layer. The first electrode has a first pad portion being localized to inside with respect to a imaginary circle whose center is at the same location as center of gravity of the polygon shape, a first extension portion that extends from the first pad portion so as to overlap the imaginary circle, a second extension portion that extends so as to overlap the imaginary circle from the first pad portion on the opposite side from the first extension portion.

Still another light emitting device of the present disclosure includes a semiconductor layer which is in a planer shape of hexagon, and a first electrode and a second electrode provided on the semiconductor layer. The first electrode has a first pad portion that is disposed near one side constituting the hexagon, a first extension portion that extends from the first pad portion along an imaginary circle whose center is at the same location as center of gravity of the hexagon, and a second extension portion that extends along the imaginary circle from the first pad portion on the opposite side from the first extension portion. The second electrode has a second pad portion that is disposed near another side facing to the one side constituting the hexagon, and more inside than the imaginary circle.

Disclosed herein is a light emitting element, wherein it is possible to provide a light emitting element with which uneven current density distribution can be further reduced.

DETAILED DESCRIPTION OF THE INVENTION

A plurality of structural elements disclosed herein may be configured as a single part which serves the purpose of a plurality of elements, on the other hand, a single structural element may be configured as a plurality of parts which serve the purpose of a single element. Further, constitutions described in some of examples and embodiments can be employed in other examples and embodiments.

The light emitting element disclosed herein has a semiconductor layer, and a first electrode and second electrode provided on the semiconductor layer.

Semiconductor Layer

The semiconductor layer is the light emitting part of the light emitting element. There are no particular restrictions on the material of this layer, but examples include InXAlYGa1-X-YN (0≤X, 0≤Y, X+Y≤1) and other such nitride semiconductor materials.

The semiconductor layer is usually made up of a plurality of layers. For example, it may be made up of a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer that is disposed in between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. The first conductivity type semiconductor layer and the second conductivity type semiconductor layer have mutually different conduction types.

The first conductivity type semiconductor layer and the second conductivity type semiconductor layer may each have a single-layer structure or a laminated structure. In the case of a laminated structure, not all of the layers constituting the first conductivity type semiconductor layer or the second conductivity type semiconductor layer need to exhibit the first conductivity type or the second conductivity type. The active layer may be either a single quantum well structure or a multiple quantum well structure formed as a thin-film that produces a quantum effect.

The semiconductor layer is usually laminated over a substrate. There are no particular restrictions on the material of the substrate, but an example is sapphire (Al2O3). The light emitting element does not necessarily have to have this substrate.

In order for the first electrode and second electrode (discussed below) to be disposed on the same face side of the semiconductor layer, either the second conductivity type semiconductor layer is disposed on the first conductivity type semiconductor layer so that part of the first conductivity type semiconductor layer is exposed, or the first conductivity type semiconductor layer is disposed on the second conductivity type semiconductor layer so that part of the second conductivity type semiconductor layer is exposed, for example.

There are no particular restrictions on the planar shape of the light emitting element and/or the semiconductor layer, but the light emitting element and/or the semiconductor layer which is in a planar shape of a circular, or a polygon at least of a pentagon is preferable. With a polygon shape, a regular polygon shape is preferable. Examples of preferable polygon shapes include pentagonal, hexagonal, octagonal, decagonal, and dodecagonal. Hexagons are particularly preferable from the standpoint of production because hexagons can be densely arranged on a substrate. The corners of the polygon shape may be rounded off. The planar shapes of the light emitting element and the semiconductor layer are preferably either the same or similar, but one, and particularly the semiconductor layer, may be one of the above-mentioned planar shapes.

A diagonal line of the top face of the semiconductor layer (that is, the maximum length or the diameter) is, for example, about a few hundred to a few thousand microns long, with about 450 to 1700 μm being preferable.

First Electrode and Second Electrode

The first electrode and second electrode provided on the semiconductor layer are preferably disposed on the same face side of the semiconductor layer. It is particularly preferable for the first electrode to be electrically connected, either directly or indirectly, to the first conductivity type semiconductor layer, and for the second electrode to be electrically connected, either directly or indirectly, to the second conductivity type semiconductor layer.

The first electrode or the second electrode is preferably disposed further to the inside than the periphery of the semiconductor layer. In other words, it is preferable for the first electrode to be surrounded by the second conductivity type semiconductor layer and/or for the second electrode to be surrounded by the first conductivity type semiconductor layer. This allows current to be diffused all the way around the first electrode or second electrode. All or part of the first electrode may be surrounded by the second electrode, and vice versa. That is, all or part of the n-side electrode may be surrounded by the p-side electrode, or all or part of the p-side electrode may be surrounded by the n-side electrode. The former arrangement is preferable when ensuring adequate surface area of the active layer is taken into account.

The first electrode has a first pad portion. In addition to this first pad portion, the first electrode preferably also has a first extension portion and a second extension portion that extend from the first pad portion. In addition to, or in place of, the first extension portion and the second extension portion, the first electrode may have a fifth extension portion that extends toward a second pad portion (discussed below).

The second electrode has a second pad portion. In addition to this second pad portion, the second electrode preferably also has a third extension portion and a fourth extension portion that extend from the second pad portion. In addition to, or in place of, the third extension portion and the fourth extension portion, the second electrode may have a sixth extension portion that extends toward the first pad portion.

First Pad Portion and Second Pad Portion

Because external connection members are connected for supplying current to the light emitting element, the first pad portion and second pad portion are members used to form a bump or to bond a wire, for example.

The first pad portion and the second pad portion are preferably localized at opposite locations of the semiconductor layer, respectively (such as opposite sides or vertexes) in plan view. For instance, the first pad portion and second pad portion are preferably disposed on the center line of the semiconductor layer, respectively (depending on the shape of the semiconductor layer, this might be a “line that passes through the center of gravity” of the polygon shape), and are more preferably disposed at locations closer to the periphery than to the center of the semiconductor layer (depending on the shape of the semiconductor layer, this might be the “center of gravity”). The term “center line of the semiconductor layer” here means a line passing through the center or center of gravity of the semiconductor layer. In this Specification, however, the center line, the line that passes through the center of gravity, the center, the center of gravity, and so forth are permitted to vary within a range of a few microns to a few dozen microns, depending on the precision with which the semiconductor layer is machined and so on.

In the case where the planar shape of the semiconductor layer is polygon, the first pad portion and the second pad portion may both be disposed opposite a vertex of the polygon shape, but from the standpoint of reducing bias in the current density distribution, they are preferably disposed opposite a side of the polygon shape, and are more preferably disposed opposite the center of a side of the polygon shape, or in other words, on a perpendicular bisector of one of the sides constituting the polygon shape. It is especially preferable for the first pad portion to be localize to the inside with respect to a first imaginary circle (discussed below). That is, this means that the first pad portion accounts for a large proportion on the inside of the first imaginary circle. The second pad portion is preferably disposed on a perpendicular bisector of one of the sides constituting the polygon shape, and particularly a hexagon.

The planar shape of the first pad portion and second pad portion can be suitably adjusted according to the size of the light emitting element, the electrode layout, and so forth. For example, it can be circular, a regular polygon shape, or another such shape. It is especially preferable, when ease of wire bonding is taken into account, for the shape to be circular or nearly circular. The size of the first pad portion and second pad portion can also be suitably adjusted according to the size of the light emitting element, the electrode layout, and so forth. For example, these portions can be substantially circular and have a diameter of about 70 to 150 μm.

First Extension Portion and Second Extension Portion

The first extension portion and second extension portion extending from the first pad portion preferably extend along a first imaginary circle to which the first pad portion is tangent on the inside. In particular, the first extension portion and second extension portion preferably extend from both sides of the first pad portion, or the second extension portion extends from the first pad portion to the opposite side. The “opposite side” here refers to the different side with respect to the line passing through the center of gravity of the first pad portion and the center of gravity of the polygon shape that is the planar shape of the semiconductor layer, for example. Consequently, in the first electrode, the first pad portion, which has a tendency for the current density to be higher at the periphery where it is disposed, can be prevented from moving locally closer to the periphery of the semiconductor layer, so this lessens the unevenness of current that occurs between the first pad portion and the periphery of the semiconductor layer. As a result, unevenness of the current density distribution can be further reduced.

The size and position of the first imaginary circle can be set as desired, as long as the first pad portion is tangent on the inside. It is especially preferable for this circle to be more to the inside than the periphery of the semiconductor layer in plan view. The center of the first imaginary circle can be set so that the distance from the first electrode to the periphery of the semiconductor layer (a side or vertex in the case where the planar shape of the semiconductor layer is polygon, for example) is uniform, so it is preferably the same as the center of the semiconductor layer, that is, the same as the center of gravity of the polygon shape that is the planar shape of the semiconductor layer. However, although the center of the first imaginary circle is said here to be the same as the center or the center of gravity of the semiconductor layer, as discussed above, it is preferable for the first imaginary circle to coincide completely with the center of the center of gravity of the semiconductor layer, but as long as no bias occurs in the current density distribution, the center may be shifted within the range of about the diameter of the first pad portion (the so-called maximum length), and preferably within the range of about the radius (seeFIG. 6E). The first imaginary circle is preferably a circle that surrounds about 55 to 80% of the total surface area of the semiconductor layer, and more preferably surrounds about 65 to 70%. In other words, the diameter of the first imaginary circle is preferably at least 65% and more preferably no more than 80% with respect to the diameter or a diagonal of the semiconductor layer, that is, the longest line passing through the center of the semiconductor layer.

The phrase “along the first imaginary circle” means being disposed on the first imaginary circle, extending while tangent to the inside or the outside of the first imaginary circle, or extending in a parallel way and separated from the first imaginary circle, etc. This portion that goes along the first imaginary circle is preferably the entire first extension portion and second extension portion, but may just be a portion thereof. It is especially preferable to be disposed on the first imaginary circle, or to extend either tangent to the outside of the first imaginary circle or separated from the outside of the first imaginary circle, which reduces current bias that occurs between the first pad portion and the periphery of the semiconductor layer. However, although the first extension portion and second extension portion are separated from the first imaginary circle, the distance thereof is preferably no more than twice the width of the first extension portion and second extension portion, and more preferably no more than 1.5 times, and even more preferably no more than equal to this width.

The first extension portion and second extension portion preferably extend to near the second pad portion of the second electrode, for example. The first extension portion and second extension portion may be linked together at their distal ends along the first imaginary circle, but when light extraction from the upper face side of the semiconductor layer is taken into account, these distal ends may separate from each other near the second pad portion so that the increase in surface area of the first extension portion and second extension portion can be kept to a minimum. The distance by which the first extension portion and second extension portion separate here is, for example, about two to six times the diameter (the so-called maximum length) of the first pad portion and/or the second pad portion around the periphery of the first imaginary circle.

The first extension portion and second extension portion are preferably disposed symmetrical to a line that passes through the center of the semiconductor layer and the first pad portion, or more precisely, a line that passes through the center of gravity of the semiconductor layer (i.e., the polygon shape) and the center of gravity of the first pad (hereinafter, the definition is same as above). That is, the first extension portion and second extension portion are preferably arc shaped. The first extension portion and second extension portion preferably have the same length and width. For example, the overall length of each is preferably about 30 to 40%, and more preferably about 35%, of the outer periphery of the semiconductor layer. The width of each is preferably about 0.5 μm to about dozen or so microns.

Fifth Extension Portion

The fifth extension portion optionally had by the first electrode preferably extends, for example, to the inside of the third extension portion and fourth extension portion of the second electrode (discussed below), that is, into the region bounded by the third extension portion and the fourth extension portion. Also, the end of the fifth extension portion may branch into two or three parts along the third extension portion and the fourth extension portion (discussed below). In other words, the distal end of the fifth extension portion preferably extends more to the inside than the first imaginary circle, that is, more to the inside than the first extension portion and the second extension portion, along the first imaginary circle, or in other words the first extension portion and/or the second extension portion. The fifth extension portion, which is closer to the first pad portion, has a tendency to have higher current density than the first extension portion and second extension portion, so the distance from the fifth extension portion to the third extension portion and the fourth extension portion is preferably greater than the distance from the first extension portion and second extension portion to the third extension portion and fourth extension portion. The term “along” here means extending in a parallel way, separated from the first imaginary circle, the first extension portion, and the second extension portion.

The two distal end branches of the fifth extension portion may extend along the first imaginary circle and be linked together, or may be separated on the second pad portion side of the second electrode. The distance at which the distal ends of the fifth extension portion are separated here is, for example, about 1.5 to 5 times the diameter (the so-called maximum length) of the first pad portion and/or the second pad portion.

The two branched parts of the fifth extension portion preferably branch in a curve to the inside. A shape such as this prevents a sudden change in the electrode shape at the branching parts. Furthermore, the two branched parts of the fifth extension portion curve to the inside and separate, which causes them to curve respectively along the third extension portion and the fourth extension portion, so the diffusion of current can be made more uniform between the fifth extension portion and the third extension portion, and the fifth extension portion and the fourth extension portion.

The two branched parts of the fifth extension portion are preferably disposed symmetrical to a line that passes through the center of the semiconductor layer and the first pad portion. That is, the two branched parts of the fifth extension portion preferably have the same length and width. For example, the overall length of each is preferably about 10 to 20%, and more preferably about 15%, of the outer periphery of the semiconductor layer. The width of each is preferably about 0.5 μm to about dozen or so microns.

Part of the fifth extension portion, or one of its three branches, may extend in a straight line.

Third Extension Portion and Fourth Extension Portion

The third extension portion and fourth extension portion extending from the second pad portion preferably have their entire length, that is, the entire second electrode, disposed more to the inside than the first imaginary circle. The third extension portion preferably extends along the first extension portion, and the fourth extension portion preferably extends along the second extension portion of the first electrode. The term “along” here means extending in a parallel way, separated from the first imaginary circle, the first extension portion, and the second extension portion. It is particularly preferable for the third extension portion and the fourth extension portion to be concentric with the first imaginary circle and to extend along a second imaginary circle to which the second pad portion is tangent on the outside.

The size and position of the second imaginary circle can be suitably set according to the position of the second pad portion. It is especially preferable for the second imaginary circle to have a diameter that is about 70 to 90%, and more preferably about 80%, of that of the first imaginary circle.

The phrase “along the second imaginary circle” means being disposed on the second imaginary circle, extending while tangent to the inside or the outside of the second imaginary circle, extending in a parallel way and separated from the second imaginary circle, etc. This portion that goes along the second imaginary circle may just be a portion of the third extension portion and the fourth extension portion, but is preferably all of them. It is especially preferable for the third extension portion and the fourth extension portion to be disposed on the second imaginary circle, and more preferable for the third extension portion and the fourth extension portion to be formed in an arc shape. The distance from the second imaginary circle to the third extension portion and the fourth extension portion here is preferably no more than two times the width of the third extension portion and the fourth extension portion, and more preferably no more than 1.5 times, or no more than equal to this width.

The third extension portion and fourth extension portion preferably extend to a position that is opposite the second pad portion, for example, to near the first pad portion of the first electrode. The third extension portion and the fourth extension portion preferably extends along the second imaginary circle, and the distal ends of the third extension portion and fourth extension portion are preferably separated on the first pad portion side of the first electrode. The distance by which the third extension portion and fourth extension portion separate here is, for example, about 1.5 to 5 times the diameter (the so-called maximum length) of the first pad portion and/or the second pad portion around the periphery of the second imaginary circle.

The third extension portion and the fourth extension portion are preferably disposed symmetrical to a line that passes through the center of gravity or the center of the semiconductor layer and the second pad portion. That is, the third extension portion and the fourth extension portion preferably have the same length and width. For example, the overall length of each is preferably about 20 to 30%, and more preferably about 25%, of the outer periphery of the semiconductor layer. The width of the third extension portion and the fourth extension portion is preferably about 1 μm to about dozen or so microns for each.

Sixth Extension Portion

The sixth extension portion optionally had by the second electrode is preferably disposed between the third extension portion and the fourth extension portion, and is preferably disposed between the branched parts of the fifth extension portion of the first electrode. In other words, the sixth extension portion preferably extends toward the first pad portion, either branching or not branching. The sixth extension portion more preferably passes through the center of the semiconductor layer, that is, the center of the first imaginary circle and the center of the second imaginary circle. The sixth extension portion may extend linearly toward the first pad portion, with its distal end disposed near the center of the semiconductor layer, or may be disposed so that its distal end branches so as to surround the center of the semiconductor layer.

The overall length of the sixth extension portion is preferably about 20 to 40% of the diameter or maximum length of the semiconductor layer, and more preferably about 25 to 35%. The width of the sixth extension portion is preferably about 1 μm to about a dozen or so microns.

Positional Relation of Extension Portions

In an embodiment, in the case where the shape of the semiconductor layer top face is hexagonal or another such polygon shape, the positions of the first to sixth extension portions preferably have the relations shown in Table 1 below (seeFIG. 1B). The values in Table 1 are for when the length of a diagonal of the semiconductor layer top face is 100%, or more specifically, 950 μm.

The closer an extension portion is to the first pad portion or second pad portion, the more the surrounding current density will tend to be higher, so it is particularly preferable for the extension portions to be disposed so that the distance between extension electrodes satisfies the relation n<q<r<s.

The first electrode and second electrode can be made from aluminum or another such metal, or an alloy of these metals. It is especially preferable to use a multilayer structure in which metals are laminated in the order of Ti/Pt/Au, CrRh/Pt/Au, or the like.

A conductive layer is preferably disposed between the semiconductor layer and the first electrode or second electrode. This conductive layer is used to allow current supplied from the first electrode or the second electrode to flow uniformly over the entire plane of the first conductivity type semiconductor layer or the second conductivity type semiconductor layer. A metal thin-film can be used as this conductive layer, but since it is disposed on the light extraction side of the light emitting element, it is preferable to use a conductive oxide layer that absorbs less light even than a metal thin-film. Examples of conductive oxides include one or more kinds of oxide of elements selected from among zinc, indium, tin, and magnesium, such as ZnO, In2O3, SnO2, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), GZO (Gallium-doped Zinc Oxide).

The light emitting element according to a Example of the present disclosure will now be described in detail through reference to the drawings. The size, positional relation, and so forth of the members shown in the drawings may be exaggerated to make the description clearer. As a general rule, names and symbols that are the same refer to members that are the same, analogous, or have the same function, and detailed descriptions of these may be omitted.

As shown inFIG. 1A, the light emitting element1according to Example 1 comprises a substrate2, a semiconductor layer5consisting of an n-type conductor layer3(a second conductivity type semiconductor layer) provided over the substrate2, an active layer, and a p-type conductor layer4(a first conductivity type semiconductor layer), in that order, an n-side electrode (a second electrode6) formed over the n-type conductor layer3, and a p-side electrode (a first electrode7) that is disposed over the p-type conductor layer4and surrounding the n-side electrode.

The substrate2and the semiconductor layer5(and particularly the p-type conductor layer4) are substantially hexagonal in plan view. The length of one side of the semiconductor layer5is approximately 480 μm and the length of a diagonal is approximately 960 μm.

The first electrode7is formed on the p-type conductivity layer4. A light transmissive conductive layer8that is formed on substantially the entire surface of the p-type conductivity layer4is disposed between the second electrode6and the p-type conductivity layer4. The first electrode7is electrically connected to the p-type conductivity layer4via the conductive layer8.

The second electrode6is formed on the n-type conductivity layer3that is exposed by removing part of the p-type conductivity layer4and the active layer (out of the semiconductor layer5), and is electrically connected to the n-type conductivity layer3. The second electrode6is surrounded by p-type conductivity layer4and the active layer.

The semiconductor layer5, the second electrode6, and the first electrode7are covered by a protective film, except for a second pad portion6aand a first pad portion7a(discussed below).

The second electrode6and the first electrode7respectively includes the second pad portion6aand the first pad portion7a, which are electrically connected to an external circuit. The second pad portion6aand the first pad portion7aare respectively disposed at one end and the other end on the center line of the semiconductor layer5. This center line is parallel to one side of the semiconductor layer5, and is a line that passes through the center of the semiconductor layer5, that is, the center of gravity of a polygon shape (such as a regular hexagon). The second pad portion6aand the first pad portion7aare substantially circular in shape, having a diameter of approximately 100 μm. The distance between the second pad portion6aand the first pad portion7ais approximately 600 μm.

The second pad portion6aand the first pad portion7aare each disposed near a side5a(one of the sides of a hexagon), on a line that passes through the center of the side5aand is perpendicular to the side5a(a so-called perpendicular bisector).

A first extension portion7band a second extension portion7cthat extend from both sides of the first pad portion7aextend in an arc shape, and are disposed along a first imaginary circle A (seeFIG. 1B) to which the first pad portion7ais tangent on the inside, that is, substantially all of these portions are disposed on the first imaginary circle A. The first pad portion7ais offset or localized to the inside with respect to the first imaginary circle A. The first extension portion7band the second extension portion7care disposed symmetrical to a line that passes through the center of the semiconductor layer5and the first pad portion7a. The dotted line inFIG. 1B(such as the first imaginary circle A and a second imaginary circle B) are imaginary reference lines for when the first electrode and second electrode are disposed, and are not formed on the actual light emitting element.

The first imaginary circle A is within the semiconductor layer5in plan view, is concentric with the center of the semiconductor layer5, that is, with the center of gravity of the polygon shape, and has a radius of approximately 360 μm.

The first extension portion7band the second extension portion7cextend to a position that is opposite the first pad portion7a, i.e., to near the second pad portion6aof the second electrode6. The first extension portion7band the second extension portion7care separated near the second pad portion6aof the second electrode6. The distance between the first extension portion7band the second extension portion7cis about 290 μm at the periphery of the first imaginary circle A.

The first extension portion7band the second extension portion7ceach have an overall length of about 940 μm, and a width of about 5 μm.

The first electrode7has a fifth extension portion7dthat extends from the first pad portion7atoward the second pad portion6a. The fifth extension portion7dextends to the inside of a third extension portion6band a fourth extension portion6cof the second electrode6(discussed below). The end of the fifth extension portion7dextends in two branches along the third extension portion6band the fourth extension portion6c(discussed below). That is, the distal ends7d1and7d2of the fifth extension portion7dextend along the first extension portion7band the second extension portion7cmore to the inside than the first imaginary circle A, i.e., within the region bounded by the first extension portion7band the second extension portion7c.

The distal ends7d1and7d2branching off from the fifth extension portion7dare separated to each other on the side of the second pad portion6aof the second electrode6. The distance between the branched distal ends7d1and7d2of the fifth extension portion7dis about 200 μm.

The fifth extension portion7dbranches in a curve to the inside at the branching parts (see the circle C inFIG. 1).

The two branched parts of the fifth extension portion7dare disposed symmetrical to a line that passes through the center of the semiconductor layer5and the first pad portion7a. That is, the fifth extension portion7dincludes the two branched parts, its overall length is about 450 μm, and its width is about 5 μm.

The entire second electrode6, that is, the second pad portion6a, the third extension portion6b, and the fourth extension portion6c, is disposed more to the inside than the first imaginary circle A.

The third extension portion6bextends along the first extension portion7bof the first electrode7, and the fourth extension portion6cextends along the second extension portion7cof the first electrode7. More specifically, the third extension portion6band the fourth extension portion6care each formed in an arc shape by extending on the second imaginary circle B (seeFIG. 1B), which is concentric with the first imaginary circle A, to which the first pad portion7ais tangent on the outside. The third extension portion6band the fourth extension portion6care disposed symmetrical to a line that passes through the center of the semiconductor layer5and the second pad portion6adisposed on the second imaginary circle B.

The second imaginary circle B has a diameter of approximately 560 μm.

The third extension portion6band the fourth extension portion6cextend to a position opposite the second pad portion6a, such as to near the first pad portion7aof the first electrode7. The distal ends of the third extension portion6band the fourth extension portion6care separated on the first pad portion7aside of the first electrode7, on the second imaginary circle B. The distance by which the third extension portion6band the fourth extension portion6care separated is, for example, about 290 μm at the periphery of the second imaginary circle B.

The third extension portion6band the fourth extension portion6ceach have an overall length of about 700 μm, and a width of about 5 μm.

The second electrode6further has a sixth extension portion6dthat extends in a straight line from the second pad portion6atoward the first pad portion7a. The sixth extension portion6dis disposed between the third extension portion6band the fourth extension portion6c. The sixth extension portion6dis disposed on a straight line that passes through the center of the semiconductor layer5, and its distal end is disposed at the center of the semiconductor layer5.

The sixth extension portion6dhas an overall length of about 250 μm, and a width of about 5 μm.

The positions of the extension portions have the relations shown in Table 2 below (seeFIG. 1B).

TABLE 2Length between first extension portion and vertex of120 μmsemiconductor layer: mLength between first extension portion and side of60 μmsemiconductor layer: nLength between first to third extension portions: q75 μmLength between third extension portions to branched120 μmpart of fifth extension portions: rLength between sixth extension portion and branched160 μmpart of fifth extension portion: s

Modification Example 1 of Example 1

As shown inFIG. 2, the light emitting element10according to Modification Example 1 of Example 1 has the same configuration as the light emitting element1, except that the first electrode7and the second electrode6are rotated 30 degrees with respect to the center of the semiconductor layer5, and the first pad portion7aand the second pad portion6aare opposite a vertex5bof the hexagon of the semiconductor layer5.

Modification Example 2 of Example 1

As shown inFIG. 3, the light emitting element20according to Modification Example 2 of Example 1 has the same configuration as the light emitting element1, except that a second electrode16has no sixth extension portion.

Modification Example 3 of Example 1

As shown inFIG. 4, the light emitting element30according to Modification Example 3 of Example 1 has the same configuration as the light emitting element20, except that the first electrode7and the second electrode16are rotated 30 degrees with respect to the center of the semiconductor layer5, and the first pad portion7aand the second pad portion6aare opposite the vertex5bof the hexagon of the semiconductor layer5.

FIGS. 5A to 5Dare schematic views of the electrode shape in the light emitting element according to Example 2.

With the light emitting elements shown inFIGS. 5A and 5B, the configuration is substantially the same as that of the light emitting element1, etc., except that the length of a diagonal of the semiconductor layer5is approximately 1.4 mm, a first electrode57has a seventh extension portion57ethat extends in a straight line from the branching part of a fifth extension portion57dto the center of the semiconductor layer5, and a sixth extension portion56dof a second electrode56branches into two arc-shaped parts so as to surround the seventh extension portion57e. With the light emitting element inFIG. 5A, a first pad portion57aand a second pad portion56aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 5B, the first pad portion57aand the second pad portion56aare opposite the vertex5bof the semiconductor layer5.

With the light emitting elements shown inFIGS. 5C and 5D, the configuration is substantially the same as that of the light emitting elements shown inFIGS. 5A and 5B, except that a first extension portion57band a second extension portion57cof the first electrode57are linked. With the light emitting element inFIG. 5C, the first pad portion57aand the second pad portion56aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 5D, the first pad portion57aand the second pad portion56aare opposite the vertex5bof the semiconductor layer5.

FIGS. 6A to 6Dare simplified views of the electrode shape in the light emitting element according to Example 3.

With the light emitting elements shown inFIGS. 6A and 6B, the configuration is substantially the same as that of the light emitting element1, etc., except that the length of a diagonal of the semiconductor layer5is approximately 650 μm, a fifth extension portion67dof a first electrode67does not branch and extends toward a second pad portion66ato the center of the semiconductor layer5, and a second electrode66does not have a sixth extension portion. With the light emitting element inFIG. 6A, a first pad portion67aand the second pad portion66aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 6B, the first pad portion67aand the second pad portion66aare opposite the vertex5bof the semiconductor layer5.

With the light emitting elements shown inFIGS. 6C and 6D, the configuration is substantially the same as that shown inFIGS. 6A and 6B, except that a first extension portion67band a second extension portion67cof the first electrode67are linked. With the light emitting element inFIG. 6C, the first pad portion67aand the second pad portion66aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 6D, the first pad portion67aand the second pad portion66aare opposite the vertex5bof the semiconductor layer5.

The light emitting element inFIG. 6Ehas substantially the same configuration as the light emitting element inFIG. 6A, except that the first electrode67and the second electrode66are shifted from the center of the semiconductor layer5by a distance corresponding to the radius of the first pad portion67a.

FIGS. 7A to 7Fare simplified views of the electrode shape in the light emitting element according to Example 4.

With the light emitting elements shown inFIGS. 7A and 7B, the configuration is substantially the same as that of the light emitting element1, etc., except that the length of a diagonal of the semiconductor layer5is approximately 650 μm, a first extension portion77band second extension portion77cof a first electrode77are linked, no fifth extension portion is formed, no third extension portion and fourth extension portion is formed at a second electrode76, and a sixth extension portion is formed shorter. With the light emitting element inFIG. 7A, the first pad portion77aand the second pad portion76aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 7B, the first pad portion77aand the second pad portion76aare opposite the vertex5bof the semiconductor layer5.

With the light emitting elements shown inFIGS. 7C and 7D, the configuration is substantially the same as that of the light emitting elements shown inFIGS. 7A and 7B, except that the second electrode is formed only at the second pad portion76a, and no extension portions are formed. With the light emitting element inFIG. 7C, first pad portion77aand the second pad portion76aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 7D, first pad portion77aand the second pad portion76aare opposite the vertex5bof the semiconductor layer5.

The light emitting elements inFIGS. 7E and 7Fhave the same configuration as the light emitting elements inFIGS. 7A and 7B, except that the distal ends of the first extension portion77band the second extension portion77cof the first electrode77are separated, and the second pad portion76ais shifted to the end of the semiconductor layer5. With the light emitting element inFIG. 7E, the first pad portion77aand the second pad portion76aare opposite the side5aof the semiconductor layer5, and with the light emitting element inFIG. 7F, the first pad portion77aand the second pad portion76aare opposite the vertex5bof the semiconductor layer5.

Evaluation of Light Emitting Elements

As shown inFIG. 8, as a comparative example, a light emitting element was produced by disposing a first electrode87and a second electrode86in a substantially square shape on a semiconductor layer85that is substantially square in plan view. The first pad portion87aof the first electrode87is disposed so as to protrude more toward the side85aof the semiconductor layer85than the first extension portion87band the second extension portion87cextending from both sides of the first pad portion87a.

The distribution in current density was analyzed by simulation software using the finite element method for the light emitting elements1,10,20, and30of the above Examples and the light emitting element80of the comparative example. In the simulation results, a whiter coloring indicates sparser current, while a blacker coloring indicates denser current. In the case where there is no unevenness in current, this is shown as all the same coloring.

As shown inFIGS. 9A to 9C, with the light emitting element80in the comparative example, it can be seen that portions of low current density (a portion that is darker than the other portion) appear in two of the corners of the semiconductor layer on the first pad portion87aside. The reason for this is believed to be that the first electrode87is localized toward the side opposite the side85aof the semiconductor layer, so that current does not accumulate between the first pad portion87aand the side85aof the semiconductor layer. In contrast, with the light emitting elements1,10,20, and30of the Examples, there is a reduction in the portions of lower current density, and particularly with the light emitting elements1and20in which the first pad portion and second pad portion are opposite a side of the semiconductor layer, there is almost no portion of low current density, and a uniform light distribution is seen overall.

A current of 65 mA was applied to the light emitting elements1,10,20, and30and to the light emitting element80of the comparative example, and the forward voltage (Vf) was compared. These results are given in Table 3.

With the light emitting element in the Examples, Vf is reduced over that of the light emitting element in the comparative example. In particular, with the light emitting elements1and20in which the first pad portion and second pad portion are opposite a side of the semiconductor layer, the Vf value is seen to be lower even than that of the light emitting elements10and30in which the first pad portion and second pad portion are opposite a vertex of the semiconductor layer.

Furthermore, a current of 65 mA was applied to the light emitting elements1and20and to the light emitting element of the comparative example, and the light output (Po) was measured. The unit of light output is mW. The power efficiency (WPE) was also calculated from Formula (1). The unit of current is mA, and the unit of voltage is V.
Power conversion efficiency (%)={light output÷(current×voltage)}×100  (1)

These results are given in Table 4.

In regard to light output and power efficiency, an increase was noted with both of the light emitting elements1and20, in which the first pad portion and second pad portion were opposite a side of the semiconductor layer, versus the light emitting element80used in the comparative example.

FIG. 10shows the electrode shapes of the light emitting elements according to Example 5.

With the light emitting element shown inFIG. 10, the configuration is substantially the same as that of the light emitting element in Example 1, except that a substrate92and a semiconductor layer95are substantially pentagonal in plan view.

A second electrode96and a first electrode97respectively have a second pad portion96aand a first pad portion97athat are electrically connected to an external circuit. The second pad portion96aand the first pad portion97aare disposed on a line that passes through the center of gravity of the pentagonal shape of the semiconductor layer95. The first pad portion97ais disposed on a perpendicular bisector of a side95a, and the second pad portion96ais disposed opposite a vertex of the pentagon.

A first extension portion97band a second extension portion97cthat extend from the first pad portion97aextend in an arc shape along the first imaginary circle A (seeFIG. 1B) to which the first pad portion97ais tangent on the inside. The first pad portion97ais localized to the inside with respect to the first imaginary circle A.

The first electrode97further has a fifth extension portion97dthat extends from the first pad portion97atoward the second pad portion96a. The fifth extension portion97dextends to the inside of a third extension portion96band a fourth extension portion96cof the second electrode96(discussed below). The distal ends97d1and97d2of the fifth extension portion97dbranches into two parts along the third extension portion96band the fourth extension portion96c(discussed below).

The second electrode96is such that the second pad portion96a, the third extension portion96b, and the fourth extension portion96care disposed more to the inside than the first imaginary circle A. The third extension portion96bextends along the first extension portion97bof the first electrode97, and the fourth extension portion96cextends along the second extension portion97cof the first electrode97.

The second electrode96further has a sixth extension portion96dthat extends in a straight line from the second pad portion96atoward the first pad portion97a.

With the light emitting element having this configuration, just as in Example 1, etc. good light output and power efficiency are obtained.

A light emitting element according to the present disclosure can be suitably employed for various lighting apparatuses, in particular, a light source for lighting, an LED display, backlight source for a liquid crystal display device, signals, a lighted switch, various sensors, various indicators, an auxiliary light source for moving image, other consumer light sources, or the like.