LIGHT EMITTING DIODE DEVICE AND LIGHT EMITTING APPARATUS

A light emitting diode device includes an epitaxial layered structure and first and second electrodes that are disposed on the epitaxial layered structure. The second electrode includes a body portion and at least one extending portion connected to the body portion and extending in a direction away from the body portion. The extending portion includes at least one curved section. A projection of the curved section on the epitaxial layered structure includes first and second curved sides that are opposite to each other and that are curved in an identical direction. The first curved side has a first imaginary center of curvature, and the second curved side has a second imaginary center of curvature. A distance between the first imaginary center of curvature and the second imaginary center of curvature is equal to or smaller than 5 μm.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Invention Patent Application No. 202111395331.6, filed on Nov. 23, 2021. The entire content of the Chinese patent application is incorporated herein by reference.

FIELD

The disclosure relates to a semiconductor device, and more particularly to a light emitting diode device and a light emitting apparatus including the same.

BACKGROUND

Light emitting diodes (LEDs) are usually made of semiconductor materials such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), etc. An LED includes a P-N junction having a light emitting property. By applying a forward bias to the LED, electrons flow from an N region to a P region of the LED while holes flow from the P region to the N region, then charge carriers recombine at the P-N junction to emit light. The LEDs are considered to be one of the light sources having the most potential as they offer advantages such as high luminous intensity, high efficiency, small size and long lifespan. The LEDs are widely applied in various fields in daily life, for example, lighting, signal display, backlight source, vehicle lamp and big screen display. A trend to develop an LED device with increased brightness and light emitting efficiency has emerged in recent years to meet the market's various demands of applications.

In the current LED device, a high concentration of charge carriers may easily be accumulated at connected regions between metal pad(s) and extending electrode(s) (e.g., finger electrode), causing current crowding. In particular, as the LED device ages, these connected regions (i.e., where current crowding occurs) may face a high risk of burnout, so performance of the LED device may be reduced and the LED device may even be destroyed.

Therefore, optimizing the configuration of the LED device having the extended electrode(s) so as to reduce current crowding becomes an issue awaiting to be resolved.

SUMMARY

Therefore, an object of the disclosure is to provide a light emitting diode (LED) device and a light emitting apparatus that can alleviate at least one of the drawbacks of the prior art.

According to a first aspect of the disclosure, the LED device includes an epitaxial layered structure, a first electrode and a second electrode. The epitaxial layered structure includes a first semiconductor layer, a light emitting layer and a second semiconductor layer sequentially disposed in such an order. The first electrode is disposed on the epitaxial layered structure and is electrically connected to the first semiconductor layer. The second electrode is disposed on the epitaxial layered structure, is electrically connected to the second semiconductor layer, and includes a body portion and at least one extending portion that is connected to the body portion and that extends in a direction away from the body portion. The extending portion includes at least one curved section. A projection of the curved section on the epitaxial layered structure includes a first curved side and a second curved side that are opposite to each other and that are curved in an identical direction. The first curved side has a first imaginary center of curvature and a first radius of curvature. The second curved side has a second imaginary center of curvature, and a second radius of curvature that is larger than the first radius of curvature. A distance between the first imaginary center of curvature and the second imaginary center of curvature is equal to or smaller than 5 μm.

According to a second aspect of the disclosure, the light emitting apparatus includes the aforementioned LED device.

DETAILED DESCRIPTION

Referring toFIGS.1to4, a first embodiment of a light emitting diode (LED) device1according to the disclosure includes a substrate10having a substrate surface10a, an epitaxial layered structure12having an epitaxial surface12aopposite to the substrate surface10a, a first electrode21and a second electrode22.

The substrate10may be a light-transmissible substrate, an opaque substrate or a semi-transparent substrate. In a case of the substrate10being a light-transmissible or semi-transparent substrate, light emitted from the epitaxial layered structure12may pass through the substrate10and reach a side of the substrate10opposite to the epitaxial layered structure12. The substrate10may be, but is not limited to, a flat sapphire substrate, a patterned sapphire substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate or a glass substrate.

In certain embodiments, the substrate10is a patterned substrate that a protruding configuration (not shown), which may be a monolayer structure or a multi-layered structure containing at least one light extraction layer, is disposed on. The light extraction layer may have a refractive index lower than that of the substrate10, and a thickness that is greater than half of a height of the protruding configuration, which may enhance the light exiting efficiency of the LED device1. In certain embodiments, the protruding configuration may be formed as a dome-shaped structure, and the refractive index of the light extraction layer may be smaller than 1.6. For example, the light extraction layer may be made of silicon dioxide (SiO2). In certain embodiments, the substrate10may be thinned or removed so as to form a thin film-type LED chip.

The epitaxial layered structure12is disposed on the substrate surface10aof the substrate10and includes a first semiconductor layer121, a light emitting layer122and a second semiconductor layer123that are sequentially disposed on the substrate surface10ain such order.

The first semiconductor layer121is formed on the substrate surface10aof the substrate10and may be doped with n-type dopants. For example, the first semiconductor layer121may be, but is not limited to, a gallium nitride (GaN)-based semiconductor layer doped with silicon (Si). In certain embodiments, the epitaxial layered structure12further includes a buffer layer (not shown) that is disposed between the first semiconductor layer121and the substrate10. In certain embodiments, the first semiconductor layer121may be connected to the substrate10through a bonding layer (not shown).

The light emitting layer122is disposed on the first semiconductor layer121opposite to the substrate10and may have a quantum well (QW) structure. In certain embodiments, the light emitting layer122may have a multiple quantum well (MQW) structure that includes multiple well layers and multiple barrier layers alternately and repetitively stacked. Additionally, the wavelength of the light emitted by the light emitting layer122may be determined by the composition and the thickness of the well layers. That is to say, by adjusting the composition of the well layers and the barrier layers, the light emitting layer122may emit different colors of light, such as ultraviolet light, blue light or green light.

The second semiconductor layer123is disposed on the light emitting layer122opposite to the first semiconductor layer121and may be a semiconductor layer doped with p-type dopants. For example, the second semiconductor layer123may be, but is not limited to, a GaN-based semiconductor layer doped with magnesium (Mg). Each of the first semiconductor layer121and the second semiconductor layer123may have a monolayer structure or a multi-layered structure that includes a superlattice layer. In certain embodiments, the first semiconductor layer121may be doped with p-type dopants and the second semiconductor layer123may be doped with n-type dopants, i.e., the first semiconductor layer121is a p-type semiconductor layer and the second semiconductor layer123is an n-type semiconductor layer.

The LED device1according to the disclosure may further include an electrically conductive layer14and an insulating layer16. The electrically conductive layer14is light-transmissible and is disposed on the second semiconductor layer123to spread current. In certain embodiments, a projection of the electrically conductive layer14on the substrate10substantially falls within a projection of the second semiconductor layer123on the substrate10so as to achieve a more uniform current distribution and enhance the performance of light exiting. The electrically conductive layer14may include a transparent and electrically conductive material (e.g., a transparent and electrically conductive oxide) so as to increase the reliability of the LED device1. The transparent and electrically conductive material may be, but is not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium doped zinc oxide (GZO), tungsten doped indium oxide (IWO), zinc oxide (ZnO) and combinations thereof.

The insulating layer16covers the epitaxial layered structure12and the transparent and electrically conductive layer14. In other words, the insulating layer16may be disposed on the epitaxial surface12a(i.e., in contact with the first semiconductor layer121and the second semiconductor layer123) and side surfaces of the epitaxial layered structure12that connect the epitaxial surface12aand the substrate surface10a, and may extend to be disposed on a portion of the substrate surface100athat is exposed from the epitaxial layered structure12. The insulating layer16is formed with a first opening161exposing the first semiconductor layer121and a second opening162exposing the second semiconductor layer123.

The insulating layer16may perform different functions depending on its location in the LED device1. For example, the insulating layer16covering the side surfaces of the epitaxial layered structure12may prevent electrically conductive material(s) from electrically connecting to the first semiconductor layer121and the second semiconductor layer123, thereby avoiding a short circuit of the LED device1. The insulating layer16may include a non-conductive material such as an inorganic material (e.g., silicone) or a dielectric material. Examples of the dielectric material may include, but are not limited to, aluminum oxide (AlO), silicon nitride (SiNx), silicon oxide (SiOx), titanium oxide (TiOx), magnesium fluoride (MgFx), tantalum oxide, niobium oxide, barium titanate and combinations thereof. In certain embodiments, the insulating layer16may include a diffracted Bragg reflector (DBR) that is formed out of a periodic structure of layers of two of the aforementioned materials, which are repetitively stacked.

The first electrode21is disposed on the epitaxial layered structure12and is electrically connected to the first semiconductor layer121. The second electrode22is disposed on the epitaxial layered structure12and is electrically connected to the second semiconductor layer123. In this embodiment, the first electrode21fills the first opening161of the insulating layer16and is electrically connected to the first semiconductor layer121, and the second electrode22fills the second opening162of the insulating layer16and is electrically connected to the second semiconductor layer123.

The second electrode22includes a body portion221, and at least one extending portion220connected to the body portion221and extending in a direction away from the body portion221. In this embodiment, the second electrode22includes two extending portions220connected to opposite sides of the body portion221. Each of the extending portions220may include a curved section223, a connecting section222that connects the body portion221and the curved section223, and a straight section224that connects to the curved section223opposite to the connecting section222.

As shown inFIGS.1and3, a projection of the curved section223on the epitaxial layered structure12includes a first curved side2231, and a second curved side2232that are opposite to each other. The first curved side2231has a first imaginary center of curvature (C1) and a first radius of curvature (R1). The second curved side2232has a second imaginary center of curvature (C2), and a second radius of curvature (R2) that is larger than the first radius of curvature (R1). The first curved side2231and the second curved side2232are curved in an identical direction. In this embodiment, the first curved side2231and the second curved side2232are curved outwardly in a direction away from the first electrode21. A distance (S1) between the first imaginary center of curvature (C1) and the second imaginary center of curvature (C2) is equal to or smaller than 5 μm. By optimizing the design of the first curved side2231and the second curved side2232(e.g., increasing the distance (S1) between the first and second imaginary center of curvatures (C1, C2)), current crowding present in the curved section223may effectively be reduced and an area of injection of charge carriers may be expanded so that burnout of the curved section223may be prevented as the LED device1ages.

The imaginary center of curvature (C1) of the first curved side22and the imaginary center of curvature (C2) of the second curved side22are respectively referred to as centers of a first imaginary circle31completing the first curved side2231and a second imaginary circle32completing the second curved side22. To be specific, the first curved side2231is a part of the first imaginary circle31(illustrated with a dot-dashed circle) and the second curved side2232is a part of the second imaginary circle32(illustrated with a dot-dashed circle). The first imaginary center of curvature (C1) and the second imaginary center of curvature (C2) coincide with centers of the first imaginary circle31and the second imaginary circle32, respectively. The first radius of curvature (R1) of the first curved side2231and the second radius of curvature (R2) of the second curved side2232are radii of the first imaginary circle31and the second imaginary circle32, respectively.

In this embodiment, as shown inFIG.3, the first imaginary circle31is internally tangent to the second imaginary circle32. In certain embodiments, the distance (S1) between the first imaginary center of curvature (C1) and the second imaginary center of curvature (C2) is equal to or greater than 1 μm. A width of the projection of the curved section223on the epitaxial layered structure12may gradually decrease in an extending direction from the connecting section222toward the straight section224so that current crowding in the curved section223may effectively be reduced.

In certain embodiments, the first curved side2231has an arc length equal to or smaller than one fourth of a circumference of the first imaginary circle31, and the second curved side2232has an arc length equal to or smaller than one fourth of a circumference of the second imaginary circle32. In this embodiment, the LED device1has a width that is smaller than 9 mil. In such case, the arc length of the first curved side2231may be equal to or smaller than one sixth of the circumference of the first imaginary circle31, and the arc length of the second curved side2232is equal to or smaller than one fifth of the circumference of the second imaginary circle32. In certain embodiments, a proportion of the arc length of the first curved side2231to the circumference of the first imaginary circle31is smaller than a proportion of the arc length of the second curved side2232to the circumference of the second imaginary circle32. For example, the arc length of the first curved side2231may account for 10% of the circumference of the first imaginary circle31, and the arc length of the second curved side2232may account for more than 10% of the circumference of the second imaginary circle32.

In addition, a point of tangency between the first imaginary circle31and the second imaginary circle32is defined as a first point (f1), while a point on the second imaginary circle32that is the farthest from the first point (f1) is defined as a second point (f2). A first straight line (L1) connects the first point (f1) and the second point (f2). A second straight line (L2) that is perpendicular to the first straight line (L1) and passing through the second point (f2) passes through a geometric center (G) of a projection of the body portion221on the epitaxial layered structure12. In certain embodiments, the second point (f2) coincides with the geometric center (G) of the projection of the body portion221on the epitaxial layered structure12. With such arrangement, each of the extending portions220is configured to extend from the body portion221away from the second straight line (L2) and to be formed with the first curved side2231and the second curved side2232, which is conducive to improve current spreading in the LED device1and thereby reduce current crowding.

In certain embodiments, when the body portion221is located in a position offset from its intended position, the second straight line (L2) may not pass through the geometric center (G) of the projection of the body portion221on the epitaxial layered structure12(i.e., there is a distance between the second straight line (L2) and the geometric center (G) of the projection of the body portion221on the epitaxial layered structure12), which causes the width of the projection of the curved section223on the epitaxial layered structure12to gradually vary in the extending direction from the connecting section223toward the straight section224.

In certain embodiments, the centers of the first imaginary circle31and the second imaginary circle32and the geometric center (G) of the projection of the body portion221are collinear. The extending portions220extend from the body portion221in a mirror symmetric manner relative to a straight line connecting the center of the first imaginary circle31and the geometric center (G) of the projection of the body portion221. By forming two extending portions220on opposite sides of the body portion221, current spreading in the LED device1of this disclosure may be improved and current crowding reduced.

The straight section224connects to the curved section223opposite to the connecting section222. That is to say, the connecting section222, the curve section223and the straight section224are connected in such order in a direction from the body portion221toward the first electrode21. In certain embodiments, a projection of the connection section222on the epitaxial layered structure12has a width (W) that is equal to or greater than the width of the projection of the curved section223on the epitaxial layered structure12. The width (W) of the projection of the straight section224on the epitaxial layered structure12ranges from 2 μm to 4 μm. In certain embodiments, a difference between the first radius of curvature (R1) and the second radius of curvature (R2) is equal to the width (W) of the projection of the straight section224, i.e., R2−R1=W. In certain embodiments, the width (W) of the projection of the straight section224is equal to or smaller than the width of the projection of the curved section223on the epitaxial layered structure12. When the width of the projection of the curved section223on the epitaxial layered structure12gradually decreases in the extending direction from the connecting section222toward the straight section224, a projection of a connecting region between the straight section224and the curved section223has a width that is equal to a minimum width of the projection of the curved section223(i.e., a distance from a first connecting point that interconnects the first curved side2231and a projection of the straight section224on epitaxial layered structure12to a second connecting point that interconnects the second curved side2232and the projection of the straight section224). In certain embodiments, the width of the projection of the curved section223is equal to or greater than the width (W) of the projection of the straight section224and is equal to or smaller than two times the width (W) of the projection of the straight section224.

As used herein, the width of the projection of the curved section223refers to a distance between a given point on the first curved sides2231and a corresponding given point on second curved side2232, which are respectively located on a first tangent line and on a line perpendicular to the first tangent line and to the first curved side2231at the given point.

Referring toFIGS.3and4, the projection of the connecting section222on the epitaxial layered structure12includes a first connecting side2221and a second connecting side2222opposite to each other. The first connecting side2221is connected to the first curved side2231and has a third radius of curvature (R3). The second connecting side2222is connected to the second curved side2232and has a fourth radius of curvature (R4). The first connecting side2221and the second connecting side2222are curved in opposite directions. In other words, the first connecting side2221may be curved outwardly in the direction away from the first electrode21, and the second connecting side2222may be curved inwardly in a direction toward the first electrode21. The third radius of curvature (R3) and the fourth radius of curvature (R4) are smaller than the first radius of curvature (R1). In certain embodiments, each of the third radius of curvature (R3) and the fourth radius of curvature (R4) is equal to or greater than 10 μm. In certain embodiments, the third radius of curvature (R3) is equal to the fourth radius of curvature (R4). For example, each of the third radius of curvature (R3) and the fourth radius of curvature (R4) may be 10 μm or 15 μm.

Referring toFIGS.5to8, consecutive steps for manufacturing the first embodiment of the LED device1are illustrated and described as follows. It should be noted that the shadow region depicted in each ofFIGS.5to8represents an additional feature formed by a corresponding step in a given figure as compared to the previous figure.

First, referring toFIG.5, the epitaxial layered structure12that includes the first semiconductor layer121, the light emitting layer122and the second semiconductor layer123is formed on the substrate10. Then, the epitaxial layered structure12is etched in a direction from the second semiconductor layer123toward the substrate surface10auntil an opening that exposes a portion of the first semiconductor layer121is formed. In addition, a peripheral portion of the epitaxial layered structure12may selectively be etched to expose the substrate surface10a, which may facilitate a fabrication process (e.g., cutting) that follows.

Next, referring toFIG.6, the electrically conductive layer14is selectively formed on the second semiconductor layer123for spreading current and increasing the reliability of the LED device1. The electrically conductive layer14is not in contact with the first semiconductor layer121.

Next, referring toFIG.7, the insulating layer16is formed on and covers the epitaxial layered structure12, and further covers the electrically conductive layer14. The insulating layer16is formed with the first opening161and the second opening162that expose the first semiconductor layer121and the second semiconductor layer123, respectively. The insulating layer16is configured to isolate electrical conduction and protect components that are covered thereby.

Afterwards, referring toFIG.8, the first electrode21and the second electrode22formed on the insulating layer16are illustrated with different patterns. To be specific, the first electrode21is formed to be electrically connected to the first semiconductor layer121through the first opening161, and the second electrode22is formed to be electrically connected to the second semiconductor layer123through the second opening162. In certain embodiments, the body portion221of the second electrode22covers and fills the second opening162so that adhesion between the second electrode22and the electrically conductive layer14is enhanced and the second electrode22becomes difficult to be peeled off from the electrically conductive layer14.

Referring toFIGS.9to11, a second embodiment of the LED device2according to the disclosure is generally similar to the first embodiment of the LED device1, except for the configuration of the second electrode22. Specifically, the second embodiment of the LED device2has a width greater than that of the LED device1, e.g., equal to or greater than 9 mil, and the extending portion220of the second electrode22thereof is designed to have the following configuration.

Referring toFIG.10, in the second embodiment, the first curved side2231and the second curved side2232are parts of the first imaginary circle31and the second imaginary circle32(illustrated with dot-dashed circles), respectively. The first imaginary circle31is internally tangent to the second imaginary circle32. The point of tangency between the first imaginary circle31and the second imaginary circle32is defined as the first point (f1). The point on the second imaginary circle32that is the farthest from the first point (f1) is defined as the second point (f2). The first straight line (L1) connecting the first point (f1) and the second point (f2) passes through the center of the second imaginary circle32. A point on the first imaginary circle (31) that is the farthest from the first point (f1) is defined as a third point (f3). A line connecting the first point (f1) and the third point (f3) passes through the center of the first imaginary circle31. A third straight line (L3) connects the second point (f2) and the third point (f3). A fourth straight line (L4) that passes through a center of the third straight line (L3) and that is perpendicular to the third straight line (L3) passes through the geometric center (G) of the projection of the body portion221on the epitaxial layered structure12.

A fifth straight line (L5) in a horizontal direction passes through the geometric center (G) of the projection of the body portion221. Moreover, a sixth straight line (L6) is perpendicular to the fifth straight line (L5) and passes through the geometric center (G) of the projection of the body portion221on the epitaxial layered structure12. The fifth straight line (L5) coincides with the fourth straight line (L4). In this embodiment, two extending portions220extend from opposite sides of the body portion221and are arranged in a mirror symmetric manner relative to the sixth straight line (L6). In certain embodiments, each of the extending portions220extends from the body portion221along the fifth straight line (L5). In certain embodiments, the second electrode further includes a straight extending portion230extending from the body portion221along the sixth straight line (L6), and the first imaginary circle31and the second imaginary circle32are respectively tangent to two opposite sides of the straight extended portion230relative to the sixth straight line (L6).

In certain embodiments, the arc length of the first curved side2231is equal to one fourth of the circumference of the first imaginary circle31, and the arc length of the second curved side2232is equal to one fourth of the circumference of the second imaginary circle32. The distance from the first connecting point that interconnects the first curved side2231and the projection of the straight section224to the second connecting point that interconnects the second curved side2232and the projection of the straight section224is equal to the width (W) of the projection of the straight section224. A distance from a third connecting point that interconnects the projection of the connecting section222on epitaxial layered structure12and the first curved side2231to a fourth connecting point that interconnects the projection of the connecting section222and the second curved side2232(i.e., a distance between the second point (f2) and the third point (f3)) is two times the width (W) of the projection of the straight section224. In other words, the projection of the curved section223has a width of2W at an end adjacent to the connecting section222, and a width of W at an end adjacent to the straight section224. This means that the width of the projection of the curved section223is equal to or greater than the width (W) of the projection of the straight section224and is equal to or smaller than two times the width (W) of the projection of the straight section224.

In addition, the first connecting side2221and the second connecting side2222are curved in opposite directions. To be specific, as shown inFIG.11, the first connecting side2221and the second connecting side2222are disposed opposite to each other and are convex toward the fifth straight line (L5). The third radius of curvature (R3) of the first connecting side2221is equal to the fourth radius of curvature (R4) of the second connecting side2222, such as 10 μm or 15 μm.

In certain embodiments, the first imaginary circle31may not be internally tangent to the second imaginary circle32. For example, the first imaginary center of curvature (C1) of the first curved side2231may coincide with the second imaginary center of curvature (C2) of the second curved side2232. That is to say, the distance between the first imaginary center of curvature (C1) and the second imaginary center of curvature (C2) is zero. In such case, the projection of the curved section223may have a fixed width rather than a width that gradually decreases in the extending direction from the connecting section222toward the straight direction224. With such arrangement, a surface area of the projection of the curved section223may be minimized so that the influence of light absorption may greatly be reduced and the brightness of the LED device2may be increased. The diameter of the first imaginary circle31may be adjusted and predetermined according to the size of the LED device2and the environment in which the LED device2is to be used.

Referring toFIG.13, a third embodiment of the LED device according to the disclosure is generally similar to the first embodiment of the LED device1, except for the configuration of the second electrode22.

Specifically, in the third embodiment, the two extending portions220are respectively extended from left and right sides of the body portion221, in which only one extending portion220on the left side of the body portion221includes the curved section223. That is to say, the left-side extending portion220includes the connecting section222, the curved section223and the straight section224in a direction away from the body portion221. On the other hand, the right-side extending portion220only includes the connecting section222and the straight section224in the direction away from the body portion221. With this arrangement, current crowding present in the curved section223of the second electrode22may still be reduced and the area of injection of the charge carriers may also be expanded.

The disclosure also provides a light emitting apparatus that includes the LED device1and/or the LED device2as mentioned above.

It should be noted that the distance (S1) between the first imaginary center of curvature (C1) and the second imaginary center of curvature (C2) may readily be measured by those skilled in the art using any well-known equipment, such as a scanning electron microscope (SEM) or an atomic force microscope (AFM). For example, an image of the LED device is captured by the equipment. Then, three points on each of the first curved side2231and the second curved side2232are selected to form a respective one of the first imaginary circle31having the first imaginary center of curvature (C1) and the second imaginary circle32having the second imaginary center of curvature (C2) using a software installed in the equipment, followed by measurement of the distance (S1) between the first imaginary center of curvature (C1) and the second imaginary center of curvature (C2).

Additionally, in certain embodiments, each of the first curved side2231and the second curved side2232may be formed out of a plurality of line segments having gradually varied slopes.

In summary, by optimizing the configuration of the extending portion220of the second electrode22, i.e., widening the width of the curved section223, the LED device1,2of this disclosure may achieve a reduced current crowding effect and increase the area of injection of the charge carrier, thereby preventing burnout of the LED device1,2during aging.