JP3356034B2 - Nitride semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor device having a positive electrode on a p-type nitride semiconductor layer.

[0002]

2. Description of the Related Art In recent years, a light emitting device using a nitride semiconductor has attracted attention as a light emitting device capable of emitting blue light. In a conventional light emitting device using this nitride semiconductor, for example, as shown in FIG. 6, an n-type gallium nitride-based semiconductor layer 12 is grown on a sapphire substrate 11, and It has a layer structure in which a p-type gallium nitride based semiconductor layer 13 is grown via a light emitting layer 10.
In this conventional nitride semiconductor light emitting device, as shown in FIG. 6, a metal film capable of ohmic contact with the p-type gallium nitride-based semiconductor layer 13 is formed on the p-type gallium nitride-based semiconductor layer, and has a light-transmitting property. Forming a first positive electrode 15 having
The n-side negative electrode 14 is formed at a predetermined position on the exposed upper surface by removing the p-type gallium nitride-based semiconductor layer and the light emitting layer by etching to expose the upper surface of the n-type gallium nitride-based semiconductor layer. Have been. Then, in the conventional nitride semiconductor light emitting device, as shown in FIG.
A second positive electrode 116 is formed on a part of the substrate 5 for connection to an external circuit, and an insulating film 17 is formed for protecting the element except for a portion where the positive and negative electrodes are taken out.

In the conventional nitride semiconductor light emitting device configured as described above, the light emitted from the light emitting layer 10 is output through the transmissive first positive electrode.
In the portion where the second positive electrode 116 is formed, no light is output from that portion because the second positive electrode 116 is connected to an external circuit. Therefore, the light emitted immediately below the second positive electrode 116 cannot be used as effective light emission and is lost, resulting in a decrease in power efficiency. Therefore, in the conventional example, as shown in FIG.
6 and the first positive electrode 15 to form a high-resistance layer 30;
The light emission in the light-emitting layer immediately below the second positive electrode 116 was suppressed by limiting the current directly below the second positive electrode 116.

[0004]

However, in the conventional nitride semiconductor light emitting device in which the high-resistance layer 30 is formed, the number of steps for forming the high-resistance layer is increased, and the production efficiency is reduced.

Accordingly, an object of the present invention is to solve the above problems and provide a power efficient nitride semiconductor light emitting device which can be efficiently produced.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention has a structure capable of suppressing light emission in the light emitting layer immediately below the second positive electrode without forming the high resistance layer 30. As a result of diligent studies, the inventors have found that it is possible to suppress light emission in the light emitting layer immediately below the second positive electrode by performing a specific treatment using a specific metal for the first and second positive electrodes. That is, the first according to the present invention
Is a p-type gallium nitride-based semiconductor layer formed on a substrate via one or more gallium nitride-based semiconductor layers including a light-emitting layer; and a light-transmitting p-type gallium nitride-based semiconductor layer. First ohmic contact with gallium nitride based semiconductor layer
A nitride semiconductor light emitting device comprising: a positive electrode; and a second positive electrode formed on a part of the first positive electrode, wherein the nitride semiconductor light emitting device outputs light emitted through the first positive electrode. The positive electrode is
A first layer formed so as to be in contact with the first positive electrode with at least one selected from the group consisting of W, Mo, Cr and Ti as a main component, and an Au formed on the first layer are mainly composed of A laminate comprising a second layer as a component and a heat treatment,
Light emission in the light emitting layer immediately below the second positive electrode is suppressed. Further, the second nitride semiconductor light emitting device according to the present invention includes a p-type gallium nitride based semiconductor layer formed on a substrate via one or more gallium nitride based semiconductor layers including a light emitting layer; A first positive electrode having a property and in ohmic contact with the p-type gallium nitride-based semiconductor layer;
A second positive electrode formed on a part of the first positive electrode, the nitride semiconductor light emitting element outputting light emitted through the first positive electrode, wherein the second positive electrode comprises: W, Mo,
A first layer formed so as to be in contact with the first positive electrode with at least one selected from the group consisting of Cr, Ti and Ni as a main component, and a Pt formed on the first layer as a main component; The laminated body including the second layer is heat-treated to suppress light emission in the light-emitting layer immediately below the second positive electrode. In the first and second nitride semiconductor light emitting devices according to the present invention configured as described above, current injection into the light emitting layer immediately below the second positive electrode can be prevented,
Light emission in the light emitting layer immediately below the second positive electrode can be suppressed. As a result, the emission of light that is not output to the outside can be suppressed, and the power loss can be reduced, so that the power efficiency can be extremely improved.

Further, in the first and second nitride semiconductor light emitting devices according to the present invention, the second positive electrode has a temperature not lower than 250 ° C.
It is preferable that the heat treatment is performed at a predetermined temperature of 50 ° C. or less, whereby light emission in the light emitting layer immediately below the second positive electrode can be more effectively suppressed.

Further, in the first and second nitride semiconductor light emitting devices according to the present invention, the first positive electrode includes Ni, Cr,
A third layer formed mainly of at least one metal selected from the group consisting of V, Co, Pd and Ag in contact with the p-type gallium nitride based semiconductor layer, and a group consisting of Au, Pt and Ir And a fourth layer including at least one element selected from the group consisting of a main component and a fourth layer.

In the above-described nitride semiconductor light emitting device, it is preferable that the third layer is formed mainly of Ni or Co, and the fourth layer is formed mainly of Au or Pt.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The nitride semiconductor light-emitting device of the embodiment according to the present invention is a so-called semiconductor-side light-emitting device that outputs light emitted through the translucent positive electrode 15, and as shown in FIG. On a substrate 11 made of sapphire, for example, an n-type nitride semiconductor layer 12 made of AlInGaN doped with Si, for example, a light emitting layer 10 made of InGaN, and a p-type nitride semiconductor made of AlInGaN doped with Mg, for example It has a semiconductor layer structure in which the layers 13 are sequentially stacked, and is formed by forming positive and negative electrodes as follows. That is, 1
An n-side negative electrode 14 is formed on the upper surface of the n-type gallium nitride-based semiconductor layer 12, which is exposed by removing the p-type gallium nitride-based semiconductor layer and the light emitting layer to a predetermined width from one side surface (first side surface), A p-side first positive electrode 15 is formed on almost the entire upper surface of the p-type gallium nitride based semiconductor layer 13. Then, a second positive electrode 16 is formed on the first positive electrode 15 at a position distant from the negative electrode 14. Except for the openings on the negative electrode 14 and the second positive electrode 16, each electrode and each semiconductor layer are formed. An insulating film 17 is formed to cover.

Here, the nitride semiconductor light emitting device of the present embodiment has a second positive electrode 1 as shown in an enlarged view in FIG.
6, a first electrode layer 1 formed of W, Mo, Cr, Ti or Ni as a main component so as to be in contact with the first positive electrode, and a first electrode layer 1 of Au or Pt as a main component. After forming as a laminate with the second electrode layer 2 formed on the electrode layer 1, heat treatment is performed at a predetermined temperature,
Light emission in the light emitting layer 10 immediately below the second positive electrode 16 is suppressed.

In the present embodiment, the first positive electrode 15 and the second
The positive electrode 16 will be described in more detail. The light-transmitting first positive electrode 15 is formed, for example, by connecting a Ni layer containing Ni as a main component to the p-type gallium nitride-based semiconductor layer 13 by, for example,
After being formed to a thickness of 0 °, an Au layer mainly composed of Au is formed on the Ni layer to a thickness of, for example, 100 °. The laminated body of the Ni layer and the Au layer formed as described above is heated at 400 ° C.
By performing a heat treatment at a predetermined temperature in the range of 700 ° C.,
By inverting the laminated structure, the p-type gallium nitride based semiconductor layer 13
Au is mainly distributed on the side in contact with, and Ni is mainly distributed on the side remote from the p-type gallium nitride based semiconductor layer 13. The second positive electrode 16 is coated with W or the like by, for example, 200 ° by a sputtering device or the like so as to be in contact with the first positive electrode.
The first electrode layer 1 is formed by depositing Au or the like on the first electrode layer 1 to a thickness of, for example, 700 nm.
The second electrode layer 2 is formed by depositing to a thickness of 0 °. The first electrode layer 1 and the second electrode layer 2 formed as described above are subjected to a heat treatment at, for example, a temperature of 350 ° C. for 30 minutes. Incidentally, the heat treatment of the second positive electrode is performed in the above-described 35.
The effect is not limited to 0 ° C. but can be obtained by a relatively wide range of heat treatment. However, in the present invention, 25
The temperature is preferably in the range of 0 ° C to 750 ° C. Therefore,
In the present embodiment, the first positive electrode 15 and the second positive electrode 1 described above are used.
6 may be performed simultaneously. The heat treatment of the second positive electrode may be performed in the final step after the formation of the insulating film 17. Furthermore, in the case where heat is applied to the light-emitting element in a later step, heat treatment may be substituted in that step.

Next, the result of confirming the light emitting state of the nitride semiconductor light emitting device of the embodiment will be described. The first positive electrode 15 and the second positive electrode 16 in the nitride semiconductor light emitting device used for confirming the light emitting state were formed as follows. The first translucent positive electrode 15 is formed by forming a Ni layer to a thickness of 100 °, forming an Au layer to a thickness of 100 °,
It was formed by heat treatment at a temperature of 50 ° C. Further, the second positive electrode 16 forms the first electrode layer 1 by depositing W to a thickness of 200 °, and deposits Au to a thickness of 7000 ° on the second electrode layer 2 Was formed and then heat-treated at a temperature of 350 ° C. for 30 minutes.

FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a sample used for confirming a light emitting state. In this example, a light emitting element is subjected to a flip chip bonding as shown in FIG. The light emission state was confirmed from the eleventh side.
In this sample, electrodes 23a and 23 for applying a voltage to the positive and negative electrodes of the light emitting element are provided on the base substrate 21.
b, the electrodes 23a and 23b and the second positive electrode 16
And the connection with the negative electrode 14 are respectively made of conductive resin 22
a, 22b.

A voltage was applied to the thus configured sample of FIG. 2 so that the forward current of the light emitting device became 20 mA, and the light emission intensity distribution in the light emitting layer 10 was measured from the substrate 11 side. FIG. 4 shows the results. Here, FIG.
The luminous intensity for the position along the line AA ′ shown in FIG. 3 is shown, and the luminous intensity is shown as a relative value when the luminous intensity at point c is set to 1. In this sample, a
The interval between -b is immediately below the second positive electrode 16. When point a is set to 0, point b is 100 μm and point c is 175 μm.
m. As is clear from FIG. 4, in the nitride semiconductor light emitting device of the present embodiment, light emission in the light emitting layer immediately below the second positive electrode 16 is suppressed.

Next, the first positive electrode 15 and the second positive electrode 16
Table 1 shows the results of a similar study conducted by combining various metals as the (first electrode layer 1 and the second electrode layer 2).

[0017]

[Table 1]

In the column of the second positive electrode 16 in Table 1,
The elements described on the left side of (/) indicate those formed as the first electrode layer 1, and the elements described on the right side of (/)
One formed as the second electrode layer 2 is shown. Also, the first
In the column of the positive electrode 15, the elements described to the left of (/) indicate elements formed so as to be in contact with the p-type gallium nitride based semiconductor layer. In the present study, the first electrode layer 1
Is formed to a thickness of 200 °, and the second electrode layer 2
Å and heat-treated at 300 ° C. Also,
If the heat treatment temperature is in the range of 250 ° C to 750 ° C,
It was confirmed that good results were obtained.

As described in detail above, in the nitride semiconductor light emitting device of this embodiment, the second positive electrode 16 is
o, Cr, Ti or Ni
First electrode layer 1 formed to be in contact with positive electrode 15
And a second electrode layer 2 formed on the first electrode layer 1 with Au or Pt as a main component, and then heat-treated at a predetermined temperature. This allows the second
Since the current can be prevented from flowing into the light emitting layer 10 immediately below the positive electrode 16 and light emission can be suppressed, the power loss in the light emitting layer 10 immediately below the second positive electrode 16 can be reduced, and efficient light emission can be achieved. Here, the first positive electrode 15 is made of Ni
/ Pt, Co / Pt, Ni / Au and Co / Au have the same effect.

In the present invention, the first layer of the first positive electrode 15 is not limited to Ni and Co, but may be, for example, Cr, V, or A.
g, Pd. The second layer of the first positive electrode may be composed of Pt, Au.
However, for example, Ir may be used, for example. By using each of the metals exemplified above, the first positive electrode capable of making ohmic contact with the p-type gallium nitride-based semiconductor layer 13 can be formed. That is, the present invention is not particularly limited as to the metal of the first positive electrode, and the first positive electrode can be applied as long as it makes ohmic contact with the p-type gallium nitride based semiconductor layer 13. Note that the first positive electrode 15 has a temperature
It is preferable to perform heat treatment at a predetermined temperature of 50 ° C. or less,
Thereby, more effective ohmic contact can be secured.

In order to further improve the luminous efficiency and to effectively output the emitted light, the light emitting element for emitting light on the side of the semiconductor is, for example, as shown in FIG. May be arranged on a diagonal line. That is, the negative electrode 140 is formed on the surface of the n-type gallium nitride-based semiconductor layer 12 in which the p-type gallium nitride-based semiconductor layer is removed and exposed at one corner, and the positive electrode 150 is formed on the p-type gallium nitride-based semiconductor layer. Semiconductor layer 13
0, and the extraction electrode 160 is formed at a position diagonal to the negative electrode 140. With the above configuration, the same effects as those of the embodiment can be obtained, and the luminous efficiency can be further increased.

In the first and second embodiments, the nitride semiconductor layer device including the n-type gallium nitride-based semiconductor layer 12, the active layer 10, and the p-type gallium nitride-based semiconductor layer 13 has been described. It goes without saying that other semiconductor layers such as a buffer layer may be provided.
The present invention can be applied even if another semiconductor layer is provided, and has the same operation and effect as the embodiment.

[0023]

As described above in detail, in the nitride semiconductor device according to the present invention, the second positive electrode includes W,
A laminated body including a first layer mainly containing at least one selected from the group consisting of Mo, Cr, Ti and Ni and a second layer mainly containing Au or Pt is formed by heat treatment. Therefore, it is possible to prevent current from being injected into the light emitting layer immediately below the second positive electrode. Therefore, according to the present invention, without forming the high resistance layer,
Since light emission in the light emitting layer immediately below the positive electrode can be suppressed,
A power-efficient nitride semiconductor light emitting device can be manufactured efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a nitride semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a sample for confirming a light emitting state of the nitride semiconductor light emitting device of the embodiment.

FIG. 3 is a plan view of the nitride semiconductor light emitting device of the embodiment for showing a measurement position for confirming a light emitting state.

FIG. 4 is a graph showing a light emitting state of the nitride semiconductor light emitting device of the embodiment.

FIG. 5 is a plan view showing an electrode configuration of a nitride semiconductor device of a modified example according to the present invention.

FIG. 6 is a schematic sectional view showing a configuration of a conventional nitride semiconductor light emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st electrode layer, 2 ... 2nd electrode layer, 10 ... Active layer, 11 ... Substrate, 12 ... N-type gallium nitride based semiconductor layer, 13 ... P-type gallium nitride based semiconductor layer, 14 ... Negative electrode, 15: first positive electrode, 16: second positive electrode, 17: insulating film.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (5)

(57) [Claims] 1. A p-type gallium nitride-based semiconductor layer formed on a substrate via one or more gallium nitride-based semiconductor layers including a light-emitting layer; A nitride semiconductor light emitting device comprising: a first positive electrode in ohmic contact with a semiconductor layer; and a second positive electrode formed on a part of the first positive electrode, and outputting light emitted through the first positive electrode. An element, wherein the second positive electrode includes a first layer formed of at least one selected from the group consisting of W, Mo, Cr, and Ti so as to be in contact with the first positive electrode; A laminate formed on the first layer and including a second layer containing Au as a main component is heat-treated;
A nitride semiconductor light emitting device, wherein light emission in a light emitting layer immediately below the second positive electrode is suppressed. 2. A p-type gallium nitride-based semiconductor layer formed on a substrate via one or more gallium nitride-based semiconductor layers including a light-emitting layer; A nitride semiconductor light emitting device comprising: a first positive electrode in ohmic contact with a semiconductor layer; and a second positive electrode formed on a part of the first positive electrode, and outputting light emitted through the first positive electrode. An element, wherein the second positive electrode is a first layer formed so as to be in contact with the first positive electrode with at least one selected from the group consisting of W, Mo, Cr, Ti and Ni as a main component. And P formed on the first layer
A nitride semiconductor light-emitting device, wherein a laminate including a second layer containing t as a main component is heat-treated to suppress light emission in a light-emitting layer immediately below the second positive electrode. 3. The method according to claim 2, wherein the second positive electrode is at least 250 ° C. and at least 750.
The heat treatment is performed at a predetermined temperature of not more than ℃.
The nitride semiconductor light-emitting device according to any of the preceding claims. 4. The first positive electrode comprises Ni, Cr, V, C
at least one selected from the group consisting of o, Pd and Ag
A third layer formed mainly of a seed metal in contact with the p-type gallium nitride-based semiconductor layer; and a third layer formed mainly of at least one element selected from the group consisting of Au, Pt and Ir. The nitride semiconductor light-emitting device according to any one of claims 1 to 3, wherein a laminate including the four layers is heat-treated. 5. The nitride semiconductor light emitting device according to claim 4, wherein said third layer is formed mainly of Ni or Co, and said fourth layer is formed mainly of Au or Pt.