KR20060107158A - Iii-nitride semiconductor light emitting device - Google Patents

Abstract

The present invention solves the problem of current concentration at the end of the n-side or p-side electrode by providing a current blocking portion between the n-side electrode and the p-side electrode, thereby improving the reliability of the light emitting device as well as the performance of the light emitting device. .

Light Emitting Device, High Power, Electrode, Current Blocker, Reliability

Description

Group III nitride semiconductor light emitting device {Ⅲ-NITRIDE SEMICONDUCTOR LIGHT EMITTING DEVICE}

1 is a view showing a conventional group III nitride semiconductor light emitting device,

2A is a view showing an example of a plan view of a conventional light emitting device;

2B is a view showing another example of a plan view of a conventional light emitting device;

3A is a view for explaining that current concentration phenomenon occurs in the light emitting device of FIG. 2A;

FIG. 3B is a diagram illustrating that a current concentration phenomenon occurs in the light emitting device of FIG. 2B;

4 is a view showing a conventional general high power light emitting device,

5 is a view for explaining a disadvantage of a conventional general high power light emitting device;

6A and 6B illustrate an example of a group III nitride semiconductor light emitting device according to the present invention;

6C and 6D show another example of the group III nitride semiconductor light emitting device according to the present invention;

7A and 7B are views illustrating an example in which the present invention is applied to a high output light emitting device;

7C is a view showing another example in which the present invention is applied to a high power light emitting device;

7d is a view showing another example of the current interrupting unit according to the present invention;

7E is a view showing a modification of the light emitting device of FIG. 7C;

8A is a view showing another example in which the present invention is applied to a high power light emitting device;

8B is a view illustrating an example of a cross section along the A-B line of FIG. 8A,

9A is a view showing another example in which the present invention is applied to a high power light emitting device;

9B is a view illustrating an example of a cross section along the A-B line of FIG. 9A;

10A is a view showing another example of a light emitting device according to the present invention;

10B is a view showing another example of a light emitting device according to the present invention;

The present invention relates to a group III nitride semiconductor light emitting device, and more particularly, to a structure having a current blocking unit to block a current concentration phenomenon to improve the performance of the device.

Here, the group III nitride semiconductor light emitting device has a compound semiconductor layer of Al (x) Ga (y) In (1-xy) N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). Means a light emitting device, such as a light emitting diode including a, and additionally excludes that the semiconductor layer or the material itself of the other group elements, such as SiC, SiN, SiCN, CN, etc. It is not.

1 is a view showing a conventional group III nitride semiconductor light emitting device, wherein the light emitting device is an epitaxially grown n-type nitride semiconductor layer over a substrate 100, a buffer layer 200 grown on a substrate 100, and a buffer layer 200. 300, the active layer 400 epitaxially grown on the n-type nitride semiconductor layer 300, the p-type nitride semiconductor layer 500 epitaxially grown on the active layer 400 and the p-type nitride semiconductor layer 500. The n-type nitride semiconductor layer in which the front electrode 600, the p-side bonding pad 700 formed on the front electrode 600, at least the p-type nitride semiconductor layer 500 and the active layer 400 are mesa-etched and exposed ( An n-side electrode 800 is formed on the 301, and an n-type nitride semiconductor layer may be further provided between the p-type nitride semiconductor layer 500 and the front electrode 600.

2A is a view showing an example of a plan view of a conventional light emitting device, and has a front electrode 21 for facilitating current spreading, and a p-side bonding pad 22 is formed on a portion of the front electrode 21. The n-side electrode 24 is formed at one corner of the surface 23 exposed by mesa etching. In FIG. 2A, the n-side electrode 24 is located at the corner of the light emitting element, and the p-side bonding pad 22 is ideally disposed at a diagonal position of the n-side electrode 24, but the position is not much in the performance of the light emitting element. It doesn't have a big impact.

2B is a view showing another example of a plan view of a conventional light emitting device, in which an n-side electrode 24 is located on one side of the light emitting device, and a p-side bonding pad 22 is formed on the opposite side. In general, when the size of the light emitting device is 270um × 270um ~ 500um × 500um, the p-side bonding pad 22 and the n-side electrode 24 are disposed at a distance of several tens of um or more. However, as the size of the light emitting device decreases, the distance between the p-side bonding pad 22 and the n-side electrode 24 is reduced to several um to several tens of um. In this case, a phenomenon occurs in which current is concentrated in the shortest distance between the p-side bonding pad 22 and the n-side electrode 24. This phenomenon becomes larger as the current density increases.

FIG. 3A is a diagram illustrating that a current concentration phenomenon occurs in the light emitting device of FIG. 2A. When the current density is large in the light emitting device shown in FIG. 2A, the p-side bonding pad 22 and the n-side electrode 24 are illustrated. The current is concentrated at the shortest distance. This is because the sheet resistance of the p-side bonding pad 22 and the n-side electrode 24 is very small, and the sheet resistance of the front electrode 21 or the n-type nitride semiconductor layer (shown as 300 in FIG. 1) through which current flows is relatively large. . This current concentration phenomenon is a direct cause of excessively generating heat locally, thereby reducing the reliability of the light emitting device and reducing the overall brightness.

FIG. 3B is a diagram illustrating the occurrence of the current concentration phenomenon in the light emitting device of FIG. 2B. As in FIG. 3A, the current concentration phenomenon occurs at the shortest distance between the p-side bonding pad 22 and the n-side electrode 24. Done. Also in this case, the reliability of the light emitting element is deteriorated, and the luminance is lowered.

4 is a diagram illustrating a conventional general high output light emitting device, in order to implement a high output light emitting device having a large chip size, a p-side electrode having a plurality of arms 42a, 42b, and 42c on the front electrode 21. 42 is formed, and an n-side electrode 44 having a plurality of arms 44a, 44b, 44c, 44d is formed on the surface 23 which is mesa-etched and exposed. This electrode shape has an interdigitated shape while maintaining a constant distance between the arms 42a, 42b, 42c and the arms 44a, 44b, 44c, 44d to make the current density as constant as possible. have.

However, this type of electrode has a big disadvantage. FIG. 5 is a view illustrating a disadvantage of a conventional general high output light emitting device. In the case where both arms 42a and 44a are parallel ((b) regions), the current density is kept constant and shows excellent characteristics. The current concentration phenomenon occurs at the edge portion (the region) of 42a. Due to the local current concentration phenomenon, local heat generation causes deterioration in reliability of the light emitting device and also deteriorates light emission characteristics of the light emitting device.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a group III nitride semiconductor light emitting device in which a current concentration prevention pattern is formed between electrodes to improve the reliability of the light emitting device and to improve the performance of the light emitting device.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

6A and 6B illustrate an example of a group III nitride semiconductor light emitting device according to the present invention, wherein an n-type nitride semiconductor layer 20, an active layer 30, and a p-type nitride semiconductor layer ( 40) are epitaxially grown. The front electrode 61 is formed on the p-type nitride semiconductor layer 40, the p-side bonding pad 62 is formed, and the n-side electrode 64 is formed on the mesa-etched n-type nitride semiconductor layer 63. have. In the light emitting device according to the present invention, a portion of the front electrode 61 between the p-side bonding pad 62 and the n-side electrode 64 is removed to form a current interruption portion 65a. When a part of the front electrode 61 is removed, the lateral current through the p-type nitride semiconductor layer 40 having a large sheet resistance hardly flows. Therefore, it is possible to block the current flow to the part where excessive current concentration occurs, thereby preventing local current concentration. Here, the front electrode 61 is formed over the entire surface or almost the entire surface of the p-type nitride semiconductor layer 40.

6C and 6D illustrate another example of the group III nitride semiconductor light emitting device according to the present invention, wherein the p-side bonding pad 62 and the n-side electrode 64 are positioned to face each other, and the front electrode ( In addition to removing a portion of 61, the p-type nitride semiconductor layer 40, the active layer 30, and a portion of the n-type nitride semiconductor layer 20 are removed to form a current blocking portion 65b. The principle of preventing current concentration is similar to the current interruption 65a of FIG. 6B. The combination of the positions of the p-side bonding pads 62 and the n-side electrode 64 and the current interrupting portions 65a and 65b may be variously performed.

7A and 7B are diagrams illustrating an example in which the present invention is applied to a high output light emitting device, and the front electrode 21 is positioned in a region where current concentration occurs between the n-side electrode 44 and the arm 42a of the p-side electrode. A part is removed and the current interruption section 65c is formed.

FIG. 7C is a diagram illustrating another example in which the present invention is applied to a high output light emitting device, and the current blocking unit 65d removes a part of the front electrode 21 as well as the p-type nitride semiconductor layer 40, the active layer 30, A portion of the n-type nitride semiconductor layer 20 is removed.

In FIG. 7D, a portion of the front electrode 21 is removed in a region where current concentration occurs between the p-side electrode 42 and the arm 44a of the n-side electrode, so that the current interruption portion 65e is formed.

FIG. 7E illustrates an example in which the protrusion 700 for improving the light output is formed on the exposed surface for forming the current blocking unit 65c and the n-side electrode 44 in the light emitting device of FIG. 7C. The protrusion 700 may be formed by a dry etching method, a wet etching method, or the like.

FIG. 8A is a view showing another example in which the present invention is applied to a high output light emitting device, and in the case of the electrode structure shown in FIG. 4, currents at the ends of the plurality of arms 42a, 42b, 42c, 44a, 44b, 44c, 44d. While the condensation occurs, the embodiment illustrated in FIG. 8A illustrates a structure in which the number of the ends of the arms of the electrode is minimized as much as possible. That is, the n-side electrode 84 has a shape that surrounds most of the outside of the light emitting device, and then forms a circle toward the center of the light emitting device, and the p-side electrode 82 forms the n-side electrode 84 therein. After enclosing, it extends toward the center of the light emitting element. Both electrodes 82 and 84 are each provided with an appropriate number of pads for wire bonding. In the drawing, the n-side electrode 84 has wire bonding pads 841 and 842 at two corners of the light emitting device, and the p-side electrode 82 has one wire bonding pad 821 at the center of the light emitting device. Two wire bonding pads 822 and 823 are provided in contact with the p-side electrode 82 on the side opposite to the wire bonding pads 841 and 842. Current blocking portions 65f and 65g are formed in a region where current concentration occurs between the two electrodes 82 and 84. By having such a structure, the portion where current concentration occurs between the two electrodes is reduced, while the current concentration portion is inevitably provided with a current blocking portion to eliminate the current concentration phenomenon. On the other hand, the shape of the inside of the light emitting device of the two electrodes (82, 84) may have a variety of shapes, such as not only circular, but also square, triangle, hexagon. In addition, a wire may or may not be actually bonded to the wire bonding pad. This means that the wire bonding pad of the present invention may be made of a material separate from the electrode for bonding the wire, and may also be made of the same material as the electrode to simply form part of the electrode.

FIG. 8B is a view showing an example of a cross section along the A-B line of FIG. 8A, in which a wire bonding pad 821 is formed to contact the p-type nitride semiconductor layer 40. Preferably, the wire bonding pad 821 forms a Schottky contact with the p-type nitride semiconductor layer 40 instead of ohmic contact, thereby minimizing the injection of current under the wire bonding pad 821 to generate heat at the center. Can be reduced.

FIG. 9A is a diagram illustrating another example in which the present invention is applied to a high output light emitting device. Unlike FIG. 8A, a p-side electrode 92 is formed outside and an n-side electrode 94 is formed inside.

FIG. 9B is a diagram illustrating an example of a cross section along the A-B line of FIG. 9A. Since the center portion is etched to form a wire bonding pad 941, there is no p-n junction, thereby minimizing heat generation.

As described above, the wire bonding pad may be formed at various positions of the light emitting device, and FIGS. 10A to 10C illustrate examples thereof.

In the case of Fig. 10A, a wire bonding pad 102a1 is formed at one end of the p-side electrode 102a, and a current interruption portion 65h is formed near the other side of the p-side electrode 102a to prevent current concentration. It is. On the other hand, the n-side electrode 104a surrounds the entire outer periphery of the light emitting element and extends toward the center of the light emitting element.

In the case of FIG. 10B, the pad 102b1 for wire bonding is positioned in the middle of the p-side electrode 102b, and a current interruption 65i is formed near both ends of the p-side electrode 102b.

The present invention solves the problem of current concentration at the end of the n-side or p-side electrode by providing a current blocking portion between the n-side electrode and the p-side electrode, thereby improving the reliability of the light emitting device as well as the performance of the light emitting device. .

Claims (1)

A group III nitride semiconductor light emitting device comprising a current interrupting unit.

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