JPH11150297A - Nitride semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting element which has high luminous efficiency. SOLUTION: A nitride semiconductor light-emitting element is provided with a p-type gallium nitride semiconductor layer 13, formed on a translucent substrate 11 with one or two or more gallium nitride semiconductor layers 12,... containing a light-emitting layer inbetween, a first positive electrode 15 which is in ohmic contact with the layer 13, and a second positive electrode 15 formed on part of the electrode 15. In the second positive electrode 16, the layer formed in contact with the first positive electrode 15 is formed by using Au or Pt as a main component, so that this enables the light-emitting layer immediately below the electrode 16 to emit light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a nitride semiconductor light emitting device having a positive electrode in a p-type nitride semiconductor layer and outputting emitted light through a substrate.

[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. Conventional light emitting devices using this nitride semiconductor include p
So-called semiconductor-side emission type that outputs light emitted through a translucent positive electrode formed on a gallium nitride-based semiconductor layer, and outputs light emitted through a translucent sapphire substrate Broadly divided into substrate side light emitting type,
They are used properly according to the purpose. In this conventional substrate-side light emitting type nitride semiconductor light emitting device, the n-side negative electrode is formed on the exposed upper surface by exposing a part of the upper surface of the n-type gallium nitride based semiconductor layer, and the p-side negative electrode is formed. The positive electrode is
It is formed on almost the entire surface of the p-type gallium nitride based semiconductor layer.
The p-side positive electrode is a first positive electrode formed on almost the entire surface of the p-type gallium nitride-based semiconductor layer and a first positive electrode for connection to an external circuit formed on a part of the first positive electrode. It consists of two positive electrodes.

Further, in a conventional nitride semiconductor light emitting device, usually, a second semiconductor light emitting device is used to protect a semiconductor layer and an electrode layer.
After a polyimide resin film is formed except for a portion on the positive electrode and the negative electrode that is connected to an external circuit, the polyimide resin film is cured at, for example, a temperature of 300 ° C. to form a protective film. In the conventional nitride semiconductor light emitting device configured as described above, the connection portions of the second positive electrode and the negative electrode to the external circuit are respectively connected to the wiring substrate by, for example, Philip bonding,
The emitted light is output through a light-transmitting substrate. Here, in the case of performing the flip bonding, a temperature of, for example, about 250 to 300 ° C. is applied in a reflow furnace.

[0004]

However, the conventional substrate-side light emitting nitride semiconductor light emitting device requires a temperature of, for example, 250 ° C. in a protective film forming step or a flip bonding step after the second positive electrode is formed. When the above temperature is applied, there is a problem that light emission in the light emitting layer immediately below the second positive electrode becomes extremely weak as compared with other portions.
For this reason, in the substrate-side light emitting type nitride semiconductor light emitting device, the luminous efficiency could not be increased beyond a certain level.

Accordingly, an object of the present invention is to provide a nitride semiconductor light emitting device having high luminous efficiency by solving the above problems.

[0006]

According to the present invention, in order to solve the above-mentioned problems of the conventional example, as a result of earnestly studying a structure capable of sufficiently securing light emission in the light emitting layer immediately below the second positive electrode,
The present invention was completed by finding that light emission in the light emitting layer immediately below the second positive electrode can be secured by using a specific metal for the second positive electrode. That is, the nitride semiconductor light-emitting device of the present invention includes a p-type gallium nitride-based semiconductor layer formed on a light-transmitting 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 p-type gallium nitride-based semiconductor layer; and a second positive electrode formed on a part of the first positive electrode, wherein In the positive electrode, a layer formed so as to be in contact with the first positive electrode is denoted by A
By forming u or Pt as a main component, light emission of the light emitting layer immediately below the second positive electrode is enabled.

Further, in the nitride semiconductor light emitting device according to the present invention, the second positive electrode is set to a temperature of 250 ° C. or more to ensure sufficient light emission in the light emitting layer immediately below the second positive electrode.
The heat treatment is preferably performed at a predetermined temperature of 50 ° C. or lower.

In the nitride semiconductor light emitting device according to the present invention, Ni, Cr, V, Co,
A first layer formed mainly of at least one metal selected from the group consisting of Pd and Ag and in contact with the p-type gallium nitride based semiconductor layer; and a first layer formed of Au, Pt and Ir It is preferable that a stacked body including the second layer formed using at least one element as a main component is heat-treated. Thereby, good ohmic contact can be obtained between the p-type gallium nitride based semiconductor layer and the first positive electrode.

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

Further, in the nitride semiconductor light emitting device, it is preferable that the first positive electrode is heat-treated at a predetermined temperature of 400 ° C. or more and 750 ° C. or less, whereby a better ohmic contact is obtained. .

[0011]

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 substrate-side light-emitting device that outputs light emitted through a substrate 11 having a light-transmitting property. An n-type gallium nitride based semiconductor layer 12 made of, for example, AlInGaN doped with Si, for example, a light emitting layer 10 made of InGaN, and a p-type gallium nitride made of, for example, AlInGaN doped with Mg, are formed on a substrate 11 made of sapphire. It has a semiconductor layer structure in which the system semiconductor layers 13 are sequentially stacked, and is formed by forming positive and negative electrodes as follows. That is, the n-type gallium nitride-based semiconductor layer 12 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) has n
The negative electrode 14 is formed on the side, and the 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 is characterized in that the second positive electrode 16 is formed by using either Au or Pt as a main component.
Sufficient light emission in the light emitting layer 10 immediately below 6 is secured. In the present embodiment, it is preferable that the second positive electrode 16 be heat-treated at a predetermined temperature in order to secure good light emission in the light emitting layer 10 immediately below the second positive electrode 16. still,
The heat treatment of the second positive electrode 16 is performed in order to secure better light emission in the light emitting layer 10 immediately below the second positive electrode 16.
It is preferable to carry out at a predetermined temperature of 250 ° C. or more and 750 ° C. or less. In the above embodiment, the second positive electrode 1
6 is formed with Au or Pt as a main component, but the present invention is not limited to this, and at least a portion of the second positive electrode 16 that is in contact with the first positive electrode is made of either Au or Pt. It may be formed as a main component. Even with the above configuration, sufficient light emission in the light emitting layer 10 directly below the second positive electrode 16 can be ensured. The electrode configuration of the present invention is not limited to a nitride semiconductor light emitting device, but can be applied to a nitride semiconductor light receiving device. In this case, for example, a light absorption layer is formed instead of the active layer 10 of the present embodiment. In this manner, when the electrode configuration of the present invention is applied to the light receiving element and light is incident from the substrate side, the light can be sufficiently absorbed even in the light absorbing layer immediately below the second positive electrode 16, and the photoelectric conversion efficiency can be improved. Light receiving element having a high level can be formed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a nitride semiconductor light emitting device according to an embodiment of the present invention will be described. The nitride semiconductor light emitting device of the present embodiment has M
Using the OCVD method, the n-type gallium nitride based semiconductor layer 1
2. The light emitting layer 10 and the p-type gallium nitride based semiconductor layer 13 are grown. Then, the n-type gallium nitride based semiconductor layer 1
2. To remove the outer peripheral portions of the light emitting layer 10 and the p-type gallium nitride-based semiconductor layer 13 by RIE (reactive ion etching) using a chlorine-based gas, and then to form the n-side negative electrode 14 Next, the p-type gallium nitride-based semiconductor layer and the light emitting layer are removed from one side surface to a predetermined width to expose the upper surface of the n-type gallium nitride-based semiconductor layer 13. Then, the negative electrode 14, the first positive electrode 15, and the second positive electrode 16 are provided at predetermined positions.
Is formed, a protective film 17 is formed except for a portion on the negative electrode 14 and the second positive electrode 16 which is connected to an external circuit.

The first positive electrode 15 and the second positive electrode 1 of this embodiment
6 will be described in more detail.
The positive electrode 15 is formed by forming a Ni layer containing Ni as a main component to a thickness of, for example, 100 ° so as to be in contact with the p-type gallium nitride based semiconductor layer 13, and then forming Au containing Au as a main component on the Ni layer.
The layer is formed, for example, to a thickness of 500 °. The laminated body of the Ni layer and the Au layer formed as described above was heated at 400 ° C. to 700 ° C.
By performing heat treatment at a predetermined temperature in the range of ° C., the stacked structure is reversed, Au is mainly distributed on the side in contact with the p-type gallium nitride-based semiconductor layer 13, and on the side remote from the p-type gallium nitride-based semiconductor layer 13. Ni is mainly distributed.
The second positive electrode 16 is formed on the first positive electrode 15 by depositing Au to a thickness of 7000 ° using a sputtering device or the like. Then, using a dryer,
Heat treatment was performed at a temperature of 300 ° C. for 45 minutes to produce a nitride semiconductor light emitting device of an example.

The nitride semiconductor light emitting device of the embodiment prepared as described above was subjected to flip chip bonding as shown in FIG. 2, and the light emitting state was confirmed from the substrate 11 side.
In this sample, electrodes 23a and 23b for applying a voltage to the positive and negative electrodes of the light emitting element were placed on the wiring board 21.
The electrodes 23a and 23b are connected to the second positive electrode 16 and the negative electrode 14, respectively.
22b.

A voltage was applied to the thus configured sample of FIG. 2 so that the forward current of the light emitting element 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. 4 shows the emission intensity at the position along the line AA ′ shown in FIG.
It is shown as a relative value when In this sample, the space between a and b is immediately below the second positive electrode 16. Also,
Assuming that point a is 0, point b is 100 μm and point c is 1
75 μm. In FIG. 4, as a comparative example, a Ni layer is formed as the second positive electrode 16 on the side in contact with the first positive electrode to a thickness of 200 °, and then Au is deposited at 7000 nm.
The configuration is the same as that of the present embodiment, except that it is formed to a thickness of Å.

As is apparent from the emission intensity distribution shown in FIG. 4, in the nitride semiconductor light emitting device of this embodiment, the light emission in the light emitting layer immediately below the second positive electrode 16 can be increased as compared with the comparative example. . That is, in the nitride semiconductor light emitting device of the comparative example, due to the thermal stress of 300 ° C., a uniform current does not flow through the first positive electrode, but concentrates on the first positive electrode portion where the second positive electrode is not formed. As a result, no current is injected into the light emitting layer immediately below the second positive electrode, so that the light emitting intensity in the light emitting layer immediately below the second positive electrode becomes very weak. On the other hand, in the nitride semiconductor light emitting device of the present embodiment, even when a thermal stress is applied, the current flowing through the first positive electrode can be flowed almost uniformly immediately below the second positive electrode. The light emission intensity of the light emitting layer immediately below the positive electrode can be maintained at a certain level or more. In the nitride semiconductor light emitting device of this embodiment, the light emission intensity of the portion a is lower than that of the portion c because the portion a is farther from the negative electrode 14 than the portion c. It is considered that the injected current is reduced due to the resistance of the system semiconductor layer 12.

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).

[0019]

[Table 1]

In Table 1, the circles indicate that good light emission was observed in the light emitting layer immediately below the second positive electrode, and the crosses indicate that the light emission intensity was weak. Table 1
In the column of the second positive electrode 16, the elements described on the left side of (/) indicate those formed as the first electrode layer 1,
The elements described on the right side of (/) indicate those formed as the second electrode layer 2. Further, in the column of the first positive electrode 15, the elements described on the left side of (/) indicate elements formed so as to be in contact with the p-type gallium nitride based semiconductor layer. still,
In the present study, the first electrode layer 1 was formed to a thickness of 200 °, the second electrode layer 2 was formed to a thickness of 7000 °,
Heat treatment was performed at 300 ° C. The heat treatment temperature is 250
It was confirmed that good results were obtained when the temperature was in the range of 750 ° C to 750 ° C.

As described in detail above, in the nitride semiconductor light emitting device of the present embodiment, the second positive electrode 16 is formed by using Au or Pt as a main component and then heat-treated at a predetermined temperature. As a result, current can be injected into the light emitting layer 10 immediately below the second positive electrode 16, and the light emitting layer 10 immediately below the second positive electrode 16 can also emit light sufficiently.
Here, the first positive electrode 15 is made of Ni / Pt, Co / Pt,
Both 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, Ag.
Alternatively, the second layer of the first positive electrode may be made 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 the above embodiments and examples, 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.

[0024]

As described above in detail, in the nitride semiconductor device according to the present invention, in the second positive electrode, a layer formed so as to be in contact with the first positive electrode is made of Au or Pt.
Is formed as a main component, light emission of the light-emitting layer immediately below the second positive electrode becomes possible. Therefore, according to the present invention, a nitride semiconductor light emitting device having extremely high luminous efficiency can be provided.

[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 cross-sectional view when the nitride semiconductor light emitting device of the embodiment is bonded to a wiring board by flip chip bonding.

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 example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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.

Claims (5)

[Claims] 1. A light-emitting device comprising a light-transmitting substrate on a light-transmitting substrate.
Alternatively, a p-type gallium nitride-based semiconductor layer formed via two or more gallium nitride-based semiconductor layers, a first positive electrode in ohmic contact with the p-type gallium nitride-based semiconductor layer, And a second positive electrode formed in a portion of the nitride semiconductor light emitting device, wherein the second positive electrode includes a layer formed so as to be in contact with the first positive electrode, containing Au or Pt as a main component. A nitride semiconductor light-emitting device characterized in that light emission of a light-emitting layer immediately below the second positive electrode is enabled by being formed. 2. The method according to claim 1, wherein the second positive electrode is at least 250 ° C. and at least 750.
2. The nitride semiconductor light-emitting device according to claim 1, wherein the nitride semiconductor light-emitting device is heat-treated at a predetermined temperature of not more than C. 3. The first positive electrode comprises Ni, Cr, V, C
at least one selected from the group consisting of o, Pd and Ag
A first layer formed mainly of a seed metal in contact with the p-type gallium nitride-based semiconductor layer; and a first layer formed mainly of at least one element selected from the group consisting of Au, Pt and Ir. 3. The nitride semiconductor light-emitting device according to claim 1, wherein a laminate including the two layers is heat-treated. 4. The nitride semiconductor light emitting device according to claim 3, wherein said first layer is formed mainly of Ni or Co, and said second layer is formed mainly of Au or Pt. 5. The method according to claim 1, wherein the first positive electrode is at least 400.degree.
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.