KR101615283B1 - Light emitting diode having electrode pads - Google Patents

Abstract

A light emitting diode having electrode pads is disclosed. The light emitting diode includes a substrate, a light emitting structure disposed on the substrate, the light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer, the first conductivity type semiconductor layer being isolated from the light emitting structure, An electrode pad region, a first electrode pad electrically connected to the first conductivity type semiconductor layer of the light emitting structure, a second electrode pad located on the second conductivity type semiconductor layer of the electrode pad region, And at least one upper extension connected to the pad and electrically connected to the second conductive type semiconductor layer of the light emitting structure. The electrode pad region where the second electrode pad is located is isolated from the light emitting structure, so that the current can be prevented from being concentrated near the second electrode pad.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode (LED)

The present invention relates to a light emitting diode, and more particularly to a light emitting diode having electrode pads.

BACKGROUND ART GaN-based LEDs have been used in various applications such as color LED display devices, LED traffic signals, and white LEDs since gallium nitride (GaN) -based light emitting diodes have been developed.

The gallium nitride series light emitting diode is generally formed by growing epitaxial layers on a substrate such as sapphire, and includes an n-type semiconductor layer, a p-type semiconductor layer, and an active layer interposed therebetween. On the other hand, an N-electrode pad is formed on the n-type semiconductor layer, and a P-electrode pad is formed on the p-type semiconductor layer. The light emitting diode is electrically connected to an external power source through the electrode pads. At this time, current flows from the P-electrode pad to the N-electrode pad through the semiconductor layers.

In general, since the p-type semiconductor layer has a high resistivity, the current can not be uniformly dispersed in the p-type semiconductor layer, the current is concentrated in the portion where the P-electrode pad is formed, and current flows intensively through the edge . Current crowding leads to a decrease in the luminescent area, and consequently degrades the luminous efficiency. In order to solve such a problem, a technique of forming a transparent electrode layer having a low resistivity on the p-type semiconductor layer to achieve current dispersion is used. The current flowing from the P-electrode pad is dispersed in the transparent electrode layer and flows into the p-type semiconductor layer, so that the light emitting region of the light emitting diode can be widened.

However, since the transparent electrode layer absorbs light, its thickness is limited, and therefore current dispersion is limited. In particular, current dispersion using a transparent electrode layer in a large-area light emitting diode of about 1 mm 2 or more, which is used for high output, is limited.

On the other hand, extensions extending from the electrode pads are used to facilitate current dispersion in the light emitting diode. For example, U.S. Patent No. 6,650,018 discloses that electrode contacts 117, 127, i.e., a plurality of extensions from electrode pads extend in opposite directions to enhance current dispersion.

By using such a plurality of extension parts, current can be distributed over a wide area of the light emitting diode, but a current crowding phenomenon is still present in which a current is still concentrated at a position where the electrode pads are located.

On the other hand, as the size of the light emitting diode becomes larger, the probability that a defect is included in the light emitting diode increases. For example, defects such as threading dislocations, pinholes, and the like, provide a path through which current is abruptly impeded, thereby impeding current dispersion.

U.S. Patent No. 6,650,018

A problem to be solved by the present invention is to provide a light emitting diode capable of preventing a current densification phenomenon from occurring near an electrode pad.

Another object of the present invention is to provide a light emitting diode capable of evenly distributing a current in a wide area light emitting diode.

According to an aspect of the present invention, there is provided a light emitting diode comprising: a substrate; A light emitting structure disposed on the substrate, the light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer; An electrode pad region isolated from the light emitting structure and including a first conductive semiconductor layer; A first electrode pad electrically connected to the first conductive semiconductor layer of the light emitting structure; A second electrode pad positioned on the first conductive semiconductor layer in the electrode pad region; And at least one upper extension connected to the second electrode pad and electrically connected to the second conductive semiconductor layer of the light emitting structure. Since the electrode pad region where the second electrode pad is located is isolated from the light emitting structure, it is possible to prevent current from being concentrated near the second electrode pad.

The light emitting diode may further include a connection portion connecting the upper extension portion and the second electrode pad. At this time, the connection portion may be insulated from the light emitting structure. For example, an insulating layer may be interposed between the connection portion and the light emitting structure to isolate the connection portion from the light emitting structure.

The light emitting diode may further include an insulating layer covering the second conductive semiconductor layer of the light emitting structure. The insulating layer may have at least one opening, and the at least one upper extension may be electrically connected to the second conductive semiconductor layer of the light emitting structure through the opening.

Furthermore, the light emitting diode may further include a transparent electrode layer that makes an ohmic contact with the second conductive semiconductor layer of the light emitting structure. In this case, the transparent electrode layer may be exposed by the opening of the insulating layer, and the at least one upper extension may be connected to the transparent electrode layer.

The first electrode pad may be located on the first conductivity type semiconductor layer of the light emitting structure opposite to the second electrode pad. The first lower extension may extend from the first electrode pad toward the second electrode pad. The first lower extension is electrically connected to the first conductive semiconductor layer of the light emitting structure. Furthermore, the end of the first lower extension may be closer to the second electrode pad than the first electrode pad.

In addition, the light emitting diode may further include a second lower extension extending from the first electrode pad, the second lower extension extending along an edge of the substrate.

In some embodiments, the second conductive semiconductor layer and the active layer of the light emitting structure may be divided to define at least two light emitting regions. An upper extension connected to the second electrode pad is disposed on each of the at least two light emitting regions. By dividing the light emitting structure into a plurality of light emitting regions, it is possible to prevent an excessive concentration of current in these defects even if there are defects such as pinholes or electric potential at specific positions, have.

Meanwhile, the first conductive semiconductor layer of the light emitting structure may be shared by the at least two light emitting regions. Furthermore, the first electrode pad may be positioned on the first conductive semiconductor layer of the light emitting structure opposite to the second electrode pad.

In addition, the first lower extension extending from the first electrode pad toward the second electrode pad may be located between the light emitting regions. Further, the first lower extension and the upper extensions may be parallel to each other.

In some embodiments, the light emitting diode may further include an insulating layer disposed between the first conductive semiconductor layer and the second electrode pad in the electrode pad region.

According to embodiments of the present invention, since the second electrode pad is located on the isolated electrode pad region from the light emitting structure, current can be prevented from being concentrated near the second electrode pad. Also, in the case of a large-area light emitting diode, current is liable to concentrate in defects in the semiconductor layer such as pinholes and actual electric fields. However, by dividing the light emitting structure into a plurality of light emitting regions, .

1 is a plan view illustrating a light emitting diode according to an embodiment of the present invention.
Figures 2a, 2b and 2c are cross-sectional views taken along the perforations AA, BB and CC, respectively, of Figure 1.
3A to 3E are plan views illustrating a method of manufacturing a light emitting diode according to an exemplary embodiment of the present invention.
4 is a plan view illustrating a light emitting diode according to another embodiment of the present invention.
5 is a plan view illustrating a light emitting diode according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, and the like of the components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

FIG. 1 is a plan view for explaining a light emitting diode according to an embodiment of the present invention, and FIGS. 2a, 2b and 2c are sectional views taken along the perforated lines A-A, B-B and C-C, respectively,

Referring to FIGS. 1 and 2A to 2C, the light emitting diode includes a substrate 21, a light emitting structure including light emitting regions LE1 and LE2, an electrode pad region EP isolated from the light emitting structure, Pad 35, second electrode pad 33 and upper extensions 33a. The light emitting diode may include a transparent electrode layer 29, an insulating layer 31, connecting portions 33b, a first lower extension portion 35a, and second lower extension portions 35b. The light emitting structure includes a first conductive semiconductor layer 23, an active layer 25 and a second conductive semiconductor layer 27. The electrode pad region EP includes a first conductive semiconductor layer 23 ).

The substrate 11 is not particularly limited, and may be, for example, a sapphire substrate. The light emitting structure and the electrode pad region EP are located on the substrate 21.

The first conductivity type semiconductor layer 23 is located on the substrate 21 and the second conductivity type semiconductor layer 27 is located on the first conductivity type semiconductor layer 23, And the active layer 25 is interposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. The first conductive semiconductor layer 23, the active layer 25 and the second conductive semiconductor layer 27 may be formed of a gallium nitride compound semiconductor material, that is, (Al, In, Ga) N. The compositional element and the composition ratio are determined so that the active layer 25 emits light of a desired wavelength, for example, ultraviolet light or blue light.

The first conductive semiconductor layer 23 may be an n-type nitride semiconductor layer, the second conductive semiconductor layer 27 may be a p-type nitride semiconductor layer, or vice versa.

As shown in the figure, the first conductive semiconductor layer 23 and / or the second conductive semiconductor layer 27 may be formed as a single layer or may have a multi-layer structure. In addition, the active layer 25 may have a single quantum well structure or a multiple quantum well structure. A buffer layer (not shown) may be interposed between the substrate 21 and the first conductivity type semiconductor layer 23. The semiconductor layers 23, 25, 27 may be formed using MOCVD or MBE techniques.

The second conductive semiconductor layer and the active layer of the light emitting structure may be divided to define at least two light emitting regions LE1 and LE2. These light emitting regions LE1 and LE2 may be formed to have a symmetrical structure, and such a dividing process may be performed by a mesa etching process. The indent portion 30b is formed by the mesa etching process so that the second conductivity type semiconductor layer 27 and the active layer 25 can be divided into two regions. In addition, the side surfaces of the light emitting structure formed by the mesa etching process may have an inclination angle within a range of 30 to 70 degrees with respect to the surface of the substrate 21. The first conductive semiconductor layer 23 of the light emitting regions LE1 and LE2 may be shared by the light emitting regions, and therefore, the first conductive semiconductor layer 23 may be interposed between the light emitting regions. Lt; / RTI >

Further, the transparent electrode layer 29 may be positioned on the second conductive semiconductor layer 29 of the light emitting structure. The transparent electrode layer 29 may be formed of ITO or Ni / Au and may be ohmically contacted with the second conductive semiconductor layer 29.

Meanwhile, the electrode pad region EP is isolated from the light emitting structure. That is, the first conductivity type semiconductor layer 23 of the electrode pad region is spaced apart from the first conductivity type semiconductor layer 23 of the light emitting structure. Therefore, the electrode pad region EP is electrically insulated from the light emitting structure. The electrode pad region EP may be isolated from the light emitting structure by a trench region TI formed in the first conductive semiconductor layer 27. [

On the other hand, the insulating layer 31 may cover the second conductivity type semiconductor layer 27 (or the transparent electrode layer 29) of the light emitting structure. The insulating layer 31 may also cover the side surfaces of the second conductivity type semiconductor layer 29 and the active layer 25 exposed by the mesa etching. Furthermore, the insulating layer 31 has openings 31a for exposing the transparent electrode layer 29 on the light emitting regions LE1 and LE2. The transparent electrode layer 29 (or the second conductivity type semiconductor layer 27) is exposed by the openings 31a. The insulating layer 31 may cover the first conductivity type semiconductor layer 23 of the electrode pad region EP and may cover the side surface of the electrode pad region EP. The insulating layer 31 is not particularly limited as long as it is a transparent material through which the light generated in the active layer 25 can be transmitted. For example, the insulating layer 31 may be formed of SiO ₂ .

The first electrode pad 35 may be positioned on the exposed first conductive semiconductor layer 23 of the light emitting structure and the second electrode pad 33 may be positioned on the electrode pad region EP. do. The first electrode pad 35 may be located opposite to the second electrode pad 33 as shown in the figure. The first and second electrode pads 35 and 33 are bonding pads for bonding wires, and have a relatively large area to bond the wires.

The first electrode pad 35 is electrically connected to the first conductive semiconductor layer 23. Also, the first lower extension 35a may extend from the first electrode pad 35 toward the second electrode pad 33. The first lower extension portion 35a is located on the first conductivity type semiconductor layer 23 of the light emitting structure and is electrically connected to the first conductivity type semiconductor layer 23. As shown in the figure, the first lower extension 35a is located in the indent 30b between the light emitting areas LE1 and LE2, and the end of the first lower extension 35a is located near the second electrode pad 33 can do. The second lower extension portions 35b may extend from the first electrode pad 35 and the second lower extension portions 35b may extend from the first electrode pad 35 to the edge of the substrate 21 Lt; / RTI >

On the other hand, the second electrode pad 33 is located on the electrode pad area EP. The second electrode pad 33 is located on the first conductivity type semiconductor layer 23 and the insulating layer 31 is interposed between the second electrode pad 33 and the first conductivity type semiconductor layer 23, . When the insulating layer 31 is interposed between the second electrode pad 33 and the first conductivity type semiconductor layer 23, the second electrode pad can be electrically isolated from the electrode pad region EP.

On the other hand, the upper extension portions 33a are located on the light emitting regions LE1 and LE2. The upper extension portions 33a may be electrically connected to the transparent electrode layer 29 (or the second conductive type semiconductor layer 27) through the openings 31a of the insulating layer 31. [ The second conductivity type semiconductor layer 27 may be exposed through the openings 31a and the upper extension portions 33a may be directly connected to the second conductivity type semiconductor layer 27. [ The upper extensions 33a are arranged to distribute the current evenly to the second conductivity type semiconductor layer 27. For example, the upper extensions 33a may extend parallel to each other. Further, the upper extension portions 33a may be parallel to the first lower extension portion 35a. The upper extension portions 33a may be connected to the second electrode pad 33 through the connection portions 33b. Here, the connection portions 33b are insulated from the transparent electrode layer 27 (or the second conductivity type semiconductor layer 27) by the insulating layer 31. In addition, the connection portions 33a may be insulated from the side surface of the light emitting structure by the insulating layer 31. [

The electrode pads 33 and 35, the upper extension portions 33a, the connection portions 33b and the first and second lower extension portions 35a and 35b are formed of the same metal material such as Cr / Au using the same process But the present invention is not limited thereto. For example, the upper extensions 33a and the second electrode pad 33 may be formed by different processes or may be formed of different materials.

In this embodiment, the light emitting diode may have a symmetrical structure with respect to a line crossing the first electrode pad 35 and the second electrode pad 33, for example, the cut line B-B in FIG. The transparent electrode layer 29 and the upper extension portions 33a may be disposed symmetrically with respect to each other and the second lower extension portions 35b may be disposed symmetrically with respect to each other. Accordingly, the light emitting diode may exhibit the same light emission characteristics on both sides of the depressed portion 30b. Therefore, by dividing the light emitting regions into two regions, it is possible to disperse the current by mitigating the concentration of current in a defect such as a pinhole or a practical potential.

The first electrode pad 35 is positioned on the first conductive semiconductor layer 23 in the present embodiment, but when the substrate 21 is electrically conductive, the first electrode pad 35 Or may be located on the bottom surface of the substrate 21 or on the substrate 21. In this case, the second electrode pad 33 is insulated from the electrode pad region EP by the insulating layer 31.

3A to 3E are plan views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention. The method of forming the semiconductor layers 23, 25, and 27, the transparent electrode layer 29, and the insulating layer 31 is well known in the art, so a detailed description thereof will be omitted.

3A, semiconductor layers including a first conductive type semiconductor layer 23, an active layer 25, and a second conductive type semiconductor layer 27 are formed on a substrate 21. Then, the semiconductor layers are mesa-etched to expose the first conductive semiconductor layer 23. The semiconductor layers may be formed to be inclined at an inclination angle of, for example, 30 to 70 degrees. At this time, the region 30a in which the first electrode pad 35 is to be formed, the region 30b in which the first lower extension portion 35a is to be formed, and the second lower extension portions 35b are formed The first conductivity type semiconductor layer 23 of the region 30c to be formed is exposed. The area 30b in which the first lower extension 35a is to be formed is an indentation 30b that penetrates into the light emitting diode. The depressed portion 30b penetrates inward from the region 30a where the first electrode pad is to be formed. Meanwhile, the first conductivity type semiconductor layer 23 in the electrode pad region is exposed by the mesa etching process. Accordingly, the mesa etching process divides the second conductivity type semiconductor layer 27 and the active layer 23 into two luminescent regions LE1 and LE2.

Referring to FIG. 3B, the first conductive semiconductor layer 23 is etched along the periphery of the electrode pad region EP to form a trench TI. The electrode pad region EP is isolated from the first conductivity type semiconductor layer 23 of the light emitting structure including the light emitting regions LE1 and LE2 by an island shape by the trench TI.

Referring to FIG. 3C, a transparent electrode layer 29 may be formed on the second conductive semiconductor layer 27 of the light emitting regions LE1 and LE2. The transparent electrode layer 29 may be formed to have a symmetrical structure with respect to a line passing through the indentation 30b. The transparent electrode layer 29 may be formed of ITO or Ni / Au and is ohmic-contacted with the second conductive semiconductor layer 27.

Referring to FIG. 3D, an insulating layer 31 is formed on the light emitting structure. The insulating layer 31 covers the transparent electrode layer 29 of the light emitting structure and may cover the first conductive semiconductor layer 23 on the electrode pad region EP. The insulating layer 31 may cover the side surfaces of the second conductive type semiconductor layer 27 and the active layer 23 exposed by the mesa etching. The insulating layer 31 is patterned by photolithography and etching to form openings 31a for exposing the transparent electrode layer 29 on the light emitting regions LE1 and LE2. The openings 31a for exposing the transparent electrode layer 29 may be formed to be symmetrical in parallel with each other. The first conductive semiconductor layer 23 in the region where the first electrode pad 35, the first lower extension portion 35a, and the second lower extension portions 35b are to be formed is exposed.

Referring to FIG. 3E, the first electrode pad 35, the first lower extension portion 35a, and the second lower extension portions 35b are formed on the exposed first conductive semiconductor layer 23 of the light emitting structure do. The second electrode pad 33 is formed on the electrode pad region EP and the upper extension portions 33a are formed in the openings 31a. And connecting portions 33b connecting the extending portions 33a are formed.

The upper extensions 33a may be connected to the transparent electrode layer 29 and may be formed in parallel with the first lower extension 35a. Thus, a light emitting diode as shown in FIG. 1 is completed.

In the present embodiment, the light emitting structure is described as being divided into two light emitting regions LE1 and LE2. However, the present invention is not limited thereto, and the light emitting structure may be divided into a larger number of regions. In addition, although the transparent electrode layer 29 is formed after the mesa etching process, the mesa etching process may be performed after the transparent electrode layer 29 is formed. Further, although it has been described that the trench TI is formed after the mesa etching process, the trench TI may be formed first and the mesa etching process may be performed.

4 is a plan view illustrating a light emitting diode according to another embodiment of the present invention.

In the embodiment of FIG. 1, the first electrode pad 35 and the second electrode pad 33 are disposed along the long axis direction of the light emitting diode, and the recessed portion 30b is formed along the long axis direction of the light emitting diode. However, in this embodiment, the electrode pads 53 and 55 are disposed along the minor axis direction of the light emitting diode, and the depressed portion 60b is formed along the minor axis direction of the light emitting diode. The transparent electrode layer 29, the upper extensions 53a and the lower extensions 55a are arranged symmetrically with respect to the indent 60b.

The upper extensions 53a extend to the outside of the light emitting diode and surround the light emitting diode. The upper extending portions 53a have an extended portion 53b that penetrates inward from the outside of the light emitting diode. On the other hand, the lower extension portions 55a extend outward from the inside of the light emitting diode. In addition, the lower extension portions 55a may be divided into bifurcations so as to enclose the extension portion 53b in the light emission regions.

The upper extension parts 53a are connected to the transparent electrode layer 29 on the light emitting areas LE1 and LE2 through the openings 31a of the insulating layer 31 and are connected to the second electrode part 29a by the connection parts 53b. And is connected to the electrode pad 53. The connection portions 53b are insulated from the light emitting structure by the insulating layer 31. [

On the other hand, the electrode pad region EP is isolated from the light emitting structure by the trench TI as described with reference to Fig.

In this embodiment, the first lower extension (35a in Fig. 1) extending from the first electrode pad 55 to the second electrode pad 53 is omitted.

5 is a plan view illustrating a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 5, the light emitting diode according to the present embodiment is substantially similar to the light emitting diode described with reference to FIG. 4, but differs in the arrangement of the lower extension portions 65a and the upper extension portions 63a.

That is, the lower extension portions 65a extend outwardly of the light emitting diode and then enter the inner side, and the upper extension portions 63a include two extension portions on the respective transparent electrode layers 29, and these two extension portions Is disposed to surround the lower extension portion 65a which has penetrated to the inside.

The upper extensions 63a are connected to the transparent electrode layer 29 on the light emitting areas LE1 and LE2 through the openings 31a of the insulating layer 31 and are connected to the second electrode pads 63a through the connecting parts 63b. (Not shown). The connection portions 63b are insulated from the light emitting structure by the insulating layer 31. [

While several embodiments of the present invention have been described above, various embodiments and variations are possible for the arrangement of the electrode pads and extensions.

21: substrate, 23: first conductivity type semiconductor layer, 25: active layer,
27: second conductivity type semiconductor layer, 29: transparent electrode layer,
30a: a first electrode pad formation region, 30b: a recessed portion,
30c: second lower extension portion forming region, 31: insulating layer, 31a: opening portion,
33, 53: second electrode pad, 33a: upper extension part, 33b, 53b, 63b: connection part,
35, 55: first electrode pad, 35a: first lower extension,
35b: second lower extension portion, 53b: extension portion, 55a, 65a: lower extension portion,
LE1, LE2: emitting region, EP: electrode pad region, TI: trench

Claims (14)

Board;
A light emitting structure disposed on the substrate, the light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer;
An electrode pad region isolated from the light emitting structure and including a first conductive semiconductor layer;
A first electrode pad electrically connected to the first conductive semiconductor layer of the light emitting structure;
A second electrode pad positioned on the first conductive semiconductor layer in the electrode pad region; And
And at least one upper extension connected to the second electrode pad and electrically connected to the second conductive semiconductor layer of the light emitting structure. The method according to claim 1,
And a connection portion connecting the upper extension portion and the second electrode pad,
Wherein the connection portion is insulated from the light emitting structure. The method of claim 2,
And an insulating layer covering the second conductive type semiconductor layer of the light emitting structure,
Wherein the insulating layer has at least one opening,
Wherein the at least one upper extension is electrically connected to the second conductivity type semiconductor layer of the light emitting structure through the opening. The method of claim 3,
Further comprising a transparent electrode layer which makes an ohmic contact with the second conductivity type semiconductor layer of the light emitting structure,
The transparent electrode layer is exposed by the opening of the insulating layer,
And the at least one upper extension is connected to the transparent electrode layer. The method according to claim 1,
Wherein the first electrode pad is located on the first conductive type semiconductor layer of the light emitting structure opposite to the second electrode pad. The method of claim 5,
And a first lower extension portion extending from the first electrode pad toward the second electrode pad and electrically connected to the first conductive type semiconductor layer of the light emitting structure. The method of claim 6,
And an end of the first lower extension is closer to the second electrode pad than the first electrode pad. The method of claim 7,
Further comprising a second lower extension extending from the first electrode pad, the second lower extension extending along an edge of the substrate. The method according to claim 1,
The second conductive semiconductor layer and the active layer of the light emitting structure are divided to define at least two light emitting regions,
And an upper extension connected to the second electrode pad is disposed on each of the at least two light emitting regions. The method of claim 9,
Wherein the first conductive semiconductor layer of the light emitting structure is shared by the at least two light emitting regions. The method of claim 10,
Wherein the first electrode pad is located on the first conductive type semiconductor layer of the light emitting structure opposite to the second electrode pad. The method of claim 11,
Further comprising: a first lower extension extending from the first electrode pad toward the second electrode pad,
Wherein the first lower extension is located between the light emitting regions. The method of claim 12,
Wherein the first lower extension portion and the upper extension portions are parallel to each other. The method according to claim 1,
And an insulating layer disposed between the first conductive type semiconductor layer and the second electrode pad in the electrode pad region.

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