KR20110101573A - Nitride semiconductor light emitting device - Google Patents

Abstract

The present invention relates to a nitride semiconductor light emitting device which improves light extraction and device reliability by uniformly spreading current by applying the same distance and symmetrical design between each electrode when forming extension electrodes extending from each bonding pad. And a first conductivity type nitride semiconductor layer formed on the substrate to be divided into a first region and a second region of a finger structure engaged with the first region, and on the second region of the first conductivity type nitride semiconductor layer. With a predetermined interval on the active layer and the second conductivity type nitride semiconductor layer, which are formed by being laminated in sequence, the transparent electrode formed on the second conductivity type nitride semiconductor layer, and the first region of the first conductivity type nitride semiconductor layer A first electrode having a symmetrical structure and connected to each other at at least one point and having a plurality of branch electrodes in a finger structure; At least one branch electrode formed on the transparent electrode and surrounding the first electrode and extending from each side includes a second electrode formed on the same line as the branch electrode of the first electrode.

Description

Nitride semiconductor light emitting device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device for improving light extraction and device reliability by making current dispersion uniform.

In general, nitride semiconductors are group III-V semiconductor crystals having an Al x In y Ga (1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. It is widely used in light emitting devices capable of emitting light (ultraviolet to green light), especially blue light.

On the other hand, since the nitride semiconductor light emitting device is manufactured using an insulating substrate such as a sapphire substrate or a SiC substrate that satisfies the lattice matching condition for crystal growth, two electrodes connected to the p-type and n-type nitride semiconductor layers emit light. It has a horizontal structure arranged almost horizontally on the upper surface of the structure.

Recently, in order to use a nitride-based semiconductor light emitting device having such a horizontal structure as an illumination light source, high brightness is required, and in order to achieve such high brightness, a large area nitride-based semiconductor light emitting device capable of operating at a large current has been manufactured.

However, the large-area nitride semiconductor light emitting device having such a planar structure has a total current emission in comparison with the nitride semiconductor light emitting device having a vertical structure in which two electrodes are disposed on the upper and lower surfaces of the light emitting structure. Since it is not uniformly distributed in the region, there is a problem that the effective area used for light emission is not large and the luminous efficiency is low.

1 is a plan view showing a nitride semiconductor light emitting device according to the prior art, Figure 2 is a cross-sectional view showing a nitride semiconductor light emitting device along the line II-II 'of FIG.

In the nitride semiconductor light emitting device according to the prior art, as shown in FIGS. 1 and 2, the buffer layer 12 and the n-type nitride semiconductor layer 13 are sequentially stacked on the light transmissive substrate 11. In this case, the n-type nitride semiconductor layer 13 is divided into a first region and a second region of a finger structure engaged with the first region.

The substrate 11 is a substrate suitable for growing a nitride semiconductor single crystal, and is preferably formed using a transparent material including sapphire.

The buffer layer 12 is a layer for improving lattice matching with the substrate 11 before growing the n-type nitride semiconductor layer 13 on the substrate 11, and is generally formed of AlN / GaN. have.

The n-type nitride semiconductor layer 13 may be formed of a semiconductor material having an InXAlYGa1-X-YN compositional formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1).

In addition, the active layer 14 and the p-type nitride semiconductor layer 15 are sequentially stacked on the second region of the n-type nitride semiconductor 13 to form the light emitting structure 10.

The active layer 14 may be formed of an InGaN / GaN layer having a multi-quantum well structure.

The p-type nitride semiconductor layer 15 may be formed of a semiconductor material having an InXAlYGa1-X-YN compositional formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1).

In addition, an n-type electrode 16 is formed on the first region of the n-type nitride semiconductor layer 13. The n-type electrode 16 includes a plurality of n-type branch electrodes extending therefrom to efficiently distribute current when a large current is applied.

In more detail, the n-type electrode 16 includes a plurality of n-type electrodes extending to have a finger structure on a first region located at the center of the n-type nitride semiconductor layer 13 in order to minimize localized current concentration. and an n-type branch electrode.

In order to form the n-type electrode 16, a portion of the p-type nitride semiconductor layer 15 and the active layer 14 is mesa-etched with sidewalls facing the center of the substrate 11.

A plurality of n-type electrode pads 16a are formed on the n-type electrode 16.

In addition, a transparent electrode 17 is formed on the p-type nitride semiconductor layer 15. In this case, the transparent electrode 17 is formed of a conductive metal oxide such as indium tin oxide (ITO).

The p-type electrode 18 is formed on the transparent electrode 17. The p-type electrode 18 is composed of a plurality of p-type branch electrodes to increase the light emitting surface while distributing the current efficiently when a large current is applied.

The nitride semiconductor light emitting device according to the prior art configured as described above has a finger structure electrode for uniform current diffusion in designing the electrode pattern of the device to improve the electrical / optical characteristics of the high current driving light emitting device and to improve the reliability of the device. Implement

That is, the p-type electrode 18 and the n-type electrode 16 are arranged at equal intervals to design the current flow in a uniform manner, and the shape of the various electrode patterns has uniform current flow and electrical characteristics in the chip. (VF) is improving.

1 and 2, the p-type electrode 18 is disposed to surround the outermost portion of the substrate 11 and has n-type branch electrode and a finger structure extending therein from the p-type electrode 18 therein. By disposing the type electrode 16 to efficiently disperse the current during the application of a large current, the luminance characteristic can be improved and the driving voltage can be reduced.

3 is a cross-sectional view showing current dispersion in a nitride semiconductor light emitting device according to the prior art.

As shown in FIG. 3, the p-type branch electrode and the n-type electrode 16 extending from the p-type electrode 18 are disposed to efficiently disperse the current upon application of a large current, thereby improving luminance characteristics and driving voltage. Can be reduced.

However, in order to efficiently disperse current, a plurality of n-type electrodes 16 must be formed, which causes a reduction in light extraction as a reduction in the emission layer area.

In addition, as the n-type nitride semiconductor layer 13 is exposed to many areas, current crowding occurs, which affects the life of the device due to deterioration.

In addition, when the bonding pads 16a and 18a formed for the current injection of the p-type nitride semiconductor layer 15 and the n-type nitride semiconductor layer 13 are formed, a current concentration phenomenon occurs, resulting in device reliability problems and uneven current dispersion. There is a problem that causes an increase in the forward voltage (VF) of the light emitting device.

The present invention is to solve the conventional problem as described above by applying the same distance and symmetrical design between each electrode when forming the extension electrode extending from each bonding pad to uniform the diffusion of the current to improve light extraction and device reliability It is an object of the present invention to provide a nitride semiconductor light emitting device for improving.

The nitride semiconductor light emitting device according to the present invention for achieving the above object is a first conductivity type nitride semiconductor layer formed on the substrate to be divided into a first region and a second region of the finger structure meshed with the first region And an active layer and a second conductivity type nitride semiconductor layer, which are sequentially stacked on the second region of the first conductivity type nitride semiconductor layer, a transparent electrode formed on the second conductivity type nitride semiconductor layer, and the first A first electrode formed on the transparent electrode and having a symmetrical structure at regular intervals on the first region of the conductive nitride semiconductor layer and connected to each other at at least one point and having a plurality of branch electrodes in a finger structure; At least one branch electrode extending from each side while surrounding the first electrode is formed on the same line as the branch electrode of the first electrode. Characterized in that consisting of.

The nitride semiconductor light emitting device according to the present invention has the following effects.

First, an optimal electrode design for uniform current diffusion of the light emitting device can improve light extraction efficiency and reliability of the light emitting device.

Second, when forming the electrode extending from the bonding pad, the same distance and symmetrical design between the electrodes can be applied to facilitate the spread of current, and the deterioration phenomenon of the device can be improved by uniformly distributing the current as a high current driving light emitting device. have.

1 is a plan view showing a nitride semiconductor light emitting device according to the prior art
FIG. 2 is a cross-sectional view illustrating a nitride semiconductor light emitting device along line II-II ′ of FIG. 1.
3 is a cross-sectional view showing current dispersion in a nitride semiconductor light emitting device according to the related art.
4 is a plan view showing a nitride semiconductor light emitting device according to the present invention
FIG. 5 is a cross-sectional view illustrating a nitride semiconductor light emitting device along line III-III ′ of FIG. 4.
FIG. 6 is a cross-sectional view illustrating a nitride semiconductor light emitting device along line IV-IV ′ of FIG. 4.
7 is a plan view showing the current dispersion in the nitride semiconductor light emitting device according to the present invention

Hereinafter, the nitride semiconductor light emitting device according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a plan view showing a nitride semiconductor light emitting device according to the present invention, Figure 5 is a cross-sectional view showing a nitride semiconductor light emitting device along the line III-III 'of Figure 4, Figure 6 is a line IV-IV' of FIG. Sectional drawing which shows the nitride semiconductor light-emitting device which followed.

In the nitride semiconductor light emitting device according to the present invention, as shown in FIGS. 4 to 6, a buffer layer 120 is formed on a substrate 110 made of a light transmissive material, and a first conductive layer is formed on the buffer layer 120. The type nitride semiconductor layer 130 is stacked.

In this case, the first conductivity type nitride semiconductor layer 130 is divided into a first region and a second region of a finger structure that is engaged with the first region.

In more detail, the second region may include a first portion formed to surround the outermost side of the first conductivity type nitride semiconductor layer 130 and a finger structure engaged with the first region. It is divided into a central portion of the first conductivity type nitride semiconductor layer 130 and a second portion extending symmetrically to both sides with respect to the central portion.

In addition, it is preferable that both sides of the second region are formed symmetrically with respect to the center of the substrate 110. This is to cause uniform light emission to occur over the entire light emitting surface made of a large area.

The substrate 110 is made of a substrate suitable for growing a nitride semiconductor single crystal. It is preferably formed using a transparent material including sapphire, and in addition to the sapphire substrate, zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC) and aluminum nitride (AlN) can be formed.

The buffer layer 120 is a layer for improving lattice matching with the substrate 110 before growing the first conductivity type nitride semiconductor layer 130 on the substrate 110, and is generally made of AlN / GaN. Formed.

The first conductivity type nitride semiconductor layer 130 may be formed of a semiconductor material having an InXAlYGa1-X-YN compositional formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). More specifically, the first conductivity type nitride semiconductor layer 130 may be formed of a GaN layer or a GaN / AlGaN layer doped with n-type conductivity impurities. For example, Si, Ge , Sn and the like are used, and preferably Si is mainly used.

An undoped semiconductor layer (not shown) may be formed on the buffer layer 120, and the undoped semiconductor layer may be formed of undoped GaN or the like. At least one layer of the buffer layer 120 and the undoped semiconductor layer may exist on the substrate 110, or both layers may not exist.

In addition, the active layer 140 and the second conductive nitride semiconductor layer 150 are sequentially stacked on the second region of the first conductive nitride semiconductor 130 to form a light emitting structure.

The active layer 140 may be formed of an InGaN / GaN layer having a multi-quantum well structure.

The second conductivity type nitride semiconductor layer 150 may be formed of a semiconductor material having an InXAlYGa1-X-YN compositional formula (where 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1). More specifically, the second conductivity-type nitride semiconductor layer 150 may be formed of a GaN layer or a GaN / AlGaN layer doped with a p-type conductivity impurity, and examples of the p-type conductivity impurity include Mg and Zn. , Be, etc. are used, and preferably Mg is mainly used.

In addition, on the first region of the first conductivity type nitride semiconductor layer 130, the first electrodes 160 are formed in a symmetrical structure in a state where they are connected to each other. When the first electrode 160 is applied with a large current, each branch electrode 161 including a plurality of branch electrodes 161 extending therefrom to efficiently disperse current has a symmetrical structure at regular intervals. Have

In more detail, the first electrode 160 has a finger structure at regular intervals on a first region located at the center of the first conductivity type nitride semiconductor layer 130 in order to minimize localized current concentration. It includes a plurality of branch electrodes 161 extending to the left and right.

In particular, in order to form the first electrode 160 according to the present invention, a portion of the second conductivity-type nitride semiconductor layer 150 and the active layer 140 is mesa-etched to have sidewalls toward the center of the substrate 110. In addition, a part of light emitted from the active layer 140 may have an advantage in that the light integration efficiency of the device may be increased due to the angle and reflection characteristics of the mesa-etched sidewall.

The first bonding pads 160a are connected to the first electrodes 160 having symmetrical structures.

In addition, a transparent electrode 170 is formed on the second conductivity type nitride semiconductor layer 150. In this case, the transparent electrode 170 may not only be a conductive metal oxide such as indium tin oxide (ITO) but also a metal thin film having high conductivity and low contact resistance if the transmittance of the light emitting device is high. .

That is, in addition to the ITO, it may be selected from the group consisting of IZO, ZnO, CTO, In ₂ O ₃ , SnO ₂ , MgO, and CdO.

On the other hand, when the transparent electrode 170 is made of a metal thin film, it is preferable to maintain the film thickness of the metal to 50nm or less in order to secure the transmittance, for example, Ni and a film thickness of 10nm film thickness 40 nm Au may be laminated | stacked one by one.

In addition, a second electrode 180 is formed on the transparent electrode 170. The second electrode 180 is composed of a plurality of branch electrodes to increase the light emitting surface while distributing the current efficiently when a large current is applied.

More specifically, the second electrode 180 is a first branch electrode 181 positioned on the transparent electrode 170 corresponding to the first portion along the outermost side of the first conductivity type nitride semiconductor layer 130. ) And a plurality of second branch electrodes 182 positioned on the transparent electrode 170 corresponding to the second portion of the finger structure extending toward the center portion of the first conductivity type nitride semiconductor layer 130. Is done.

Here, the plurality of second branch electrodes 182 are configured to correspond to the branch electrodes 161 constituting the first electrode 160 at regular intervals.

As such, when the second electrode 180 is disposed, the resistance of the second electrode 180 is generally lower than that of the second conductivity type nitride semiconductor layer 150 or the active layer 140. Substantially, first, energization and light emission occur preferentially at the second electrode 180.

That is, in the nitride-based semiconductor light emitting device having a horizontal structure according to the present invention, the light emitting surface of the device is increased while the second electrode 180 forms the shape surrounding the first electrode 160, thereby improving the luminance characteristics of the device. Can be improved.

In addition, a plurality of second bonding pads 180a are formed on the second electrode 180.

More specifically, the second bonding pads 180a may be disposed to correspond to opposite corners on the upper surface of the quadrangular light emitting structure.

The arrangement of the first bonding pads 160a and the second bonding pads 180a not only provides stability of flip chip bonding as a whole, but is disposed at each corner of each other, so that a uniform dispersion effect of current can be expected.

7 is a plan view showing current dispersion in the nitride semiconductor light emitting device according to the present invention.

As shown in FIG. 7, the first bonding pads 160a connected to the first electrode 160 and the second bonding pads 180a connected to the second electrode 180 are symmetrically formed to form a current. The optical properties of the light emitting device may be improved by minimizing concentration and distributing current flow uniformly.

In addition, some of the first branch electrode 181 and the second branch electrode 182 of the second electrode 180 may be branch electrodes of the first electrode 160 in order to differentiate the electrode patterns of the high current driving light emitting device. The electrode is positioned on the same line as 161 so as to have a shape of an electrode pattern different from that of the related art, while the electrode is placed on the same line to facilitate the injection of current from the second electrode 180 to improve light extraction efficiency.

Table 1 below shows the Vf (V), light power (mW) and J STD (Joint Industry) in the applied current in the chip pattern of the nitride semiconductor light emitting device according to the present invention and the nitride semiconductor light emitting device of other companies. Standards) is a comparison.

LED chip pattern of the present invention Third Party LED Chip Patterns Applied current Vf (V) Power (mW) J STD Applied current Vf (V) Power (mW) J STD 50 2.65 42.12 2.72 50 2.83 34.4 3.95 80 2.77 66.77 6.19 80 2.97 55.01 7.26 120 2.93 98.9 12.8 120 3.14 82.49 11.99

As shown in Table 1, the optimal electrode design for uniform current diffusion of the light emitting device can improve the light extraction efficiency and reliability of the light emitting device.

On the other hand, it will be apparent to those skilled in the art that various changes and modifications can be made in the present invention without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be determined by the scope of the claims.

110 substrate 120 buffer layer
130: first conductivity type nitride semiconductor layer 140: active layer
150: second conductivity type nitride semiconductor layer 160: first electrode
170: transparent electrode 180: second electrode

Claims (5)

A first conductivity type nitride semiconductor layer formed on the substrate so as to be divided into a first region and a second region of a finger structure engaged with the first region;
An active layer and a second conductivity type nitride semiconductor layer which are sequentially stacked on the second region of the first conductivity type nitride semiconductor layer;
A transparent electrode formed on the second conductivity type nitride semiconductor layer;
A first electrode having a symmetrical structure and being connected to each other at at least one point and having a plurality of branch electrodes in a finger structure at regular intervals on a first region of the first conductivity type nitride semiconductor layer;
At least one branch electrode formed on the transparent electrode and enclosing the first electrode and extending from each side comprises a second electrode formed on the same line as the branch electrode of the first electrode; Semiconductor light emitting device. The nitride semiconductor light emitting device of claim 1, wherein the first and second electrodes have first and second bonding pads in a symmetrical structure with each other. 2. The first region of claim 1, wherein the second region of the first conductivity type nitride semiconductor layer is engaged with the first region and the first portion formed to surround the outermost side of the first conductivity type nitride semiconductor layer. A nitride semiconductor light emitting device according to claim 1, wherein the nitride semiconductor light emitting device is divided into a central portion of the first conductivity type nitride semiconductor layer and a second portion symmetrically extended on both sides with respect to the central portion. The nitride semiconductor light emitting device of claim 1, wherein the second conductivity type nitride semiconductor layer and the active layer have a mesa structure to expose the surface of the first conductivity type nitride semiconductor layer. The nitride electrode of claim 1, wherein the second electrode comprises: a first branch electrode positioned on a transparent electrode corresponding to a first portion along an outermost side of the first conductivity type nitride semiconductor layer; And a plurality of second branch electrodes positioned on the transparent electrode corresponding to the second portion of the finger structure extending toward the center of the layer.

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