JPS61156785A - Semiconductor luminescent device - Google Patents

Abstract

PURPOSE:To prevent the Au film from penetrating the semiconductor layer and to prevent the bad effect of the Au film by a method wherein a multilayer electrode, which is formed by laminating in order four layers consisting of a Ti film, a Ti-Pt mixed film, a Pt film and the Au film, is provided. CONSTITUTION:A P-type electrode 30 in a four-layer structure, which is constituted by laminating in order four layers consisting of a Ti film 31, a Ti-Pt mixed film 32, a Pt film 33 and an Au film 34, is provided on a P-type InGaAsP contact layer 5. When the electrode structure in such the constitution is performed a thermal treatment and is crystallized, the crystal grains in the crystal becomes smaller and are densely closed as the Ti crystal and the Pt crystal are respectively a hexagonal crystal system and a cubic crystal system and the gaps, through which the Au film pierces, decrease. By this way, the Au film is prevented from penetrating the layer of the film 34 by the film 32 obtainable a dense film quality and the bad effect of the Au film can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light emitting device, and particularly to an electrode structure of a semiconductor laser or a light emitting diode.

Recently, optical transmission has been in the spotlight, and light-emitting diodes and semiconductor lasers are used as light sources.These light sources are made of a heterojunction structure of m-v layer compound semiconductors, and are particularly difficult to transmit coherent light. Semiconductor lasers that emit light are considered to be the ideal light source for optical transmission. For example, wavelength 0.7
AIG in the ~0.9 μm band, aAs/GaAs (active layer/substrate), and InGaAs P in the wavelength band of 1 to 1.5 pm.
/InP is a well-known luminescent light source.

In such semiconductor lasers or light emitting diodes, it is desired to increase the luminous efficiency and extend the life span as much as possible, in other words, to improve the performance and reliability.

[Prior Art] FIG. 2 shows a schematic cross-sectional view of one type of buried type 1nGaAs P/InP semiconductor laser as an example of such a light emitting device, and this example has an emission wavelength of 1.3 μm. V-shaped 5ubst
rateBuried Heterostructure
e type) is an embedded laser. In the figure, 1 is n-InP
Substrate, 2 is n-1nP buff 7a layer, 3 is n-InG
aAs P active layer, 4 a p-InP cladding layer, and 5 a p-1nGaAs P contact layer.

6 is a p-InP layer (current blocking layer), and a p-electrode (+ electrode) 10 is provided on the upper surface of the contact layer 5, which is a titanium (Ti) film (11A thickness of about 1000 layers) 11.6. Platinum (PL) film (film thickness approximately 1000 people) 2. Gold (Au)
) Film 13 (M'A thickness: 3 μm) has a structure in which three layers are laminated. In addition, the n-electrode (-electrode) 20 is the InP substrate 1
It is an electrode made of gold-germanium nitride.

In such a buried laser, the laser emission is confined by the current blocking layers on both sides, and the n-InGaAs in the center
This is carried out in the P active layer 3, and is characterized in that a particularly low threshold flow can be obtained.

[Problems to be Solved by the Invention] Incidentally, in the semiconductor laser or other light emitting device exemplified above, there is no problem since the n-electrode 20 is formed on the back surface of the thick substrate, but the p-electrode IO is Since it is formed on a thin epitaxially grown layer (a layer close to the active layer), it has a large impact on reliability.

That is, if a heat treatment is performed to improve ohmic contact after depositing a Ti film, a Pt film, and an Au film, the Ti
Since the film 11 and the Pt film 12 are very thin, the plated Au
It has been found that the film diffuses through these films, reacts with the semiconductor layer, and deteriorates device characteristics.

Furthermore, Au may penetrate during operation and deteriorate the light emitting characteristics. These problems have been detected and clarified by analysis using Auger electron spectroscopy.

The reason for this is that the Ti film 11 and the Pt film 12 are deposited by electron beam evaporation, but the deposited films are in a mixed state of amorphous and polycrystalline.In particular, the Ti crystal grains have a hexagonal structure, and the C
It is presumed that Au is oriented along the axis and penetrates through the gap.

Furthermore, when observing the pinholes after these Ti films and Pt films were deposited, there were 10 +/- or more pinholes, which is also considered to be the cause of Au permeation.

On the other hand, the reason why the p-electrode 10 has a Ti-Pt- U three-layer structure is because Pt and ribs easily react with the semiconductor layer. In addition, since it easily reacts with Ti and AU, P
t is interposed therebetween.

In addition, the Ti film and Pt film were thinned to a thickness of about 1000 mm (
The reason for this is that if these layers are deposited too thickly, the thermal expansion will be significantly different from that of the semiconductor layer, causing stress and straining the semiconductor layer, which will affect the light-emitting characteristics. .

The present invention solves the problems arising from this electrode structure and proposes a light emitting device having an electrode structure that can achieve higher performance and higher reliability.

Means for solving problem U] The problem is that a Ti film + Tt-P is mixed into a film (mixing ratio: 7).
: 3 or more)

For example, this multilayer electrode is provided on a contact layer made of p -1nGaAsP.

[Function] That is, in the present invention, Ti-
A Pt mixed film is interposed between Ti and Pt.

In this case, penetration of the Au film is prevented by the Ti--Pt alloy film, which provides a dense film quality, and its adverse effects can be prevented.

[Example] An embodiment will be described in detail below with reference to one drawing.

FIG. 1 shows a VSB type 1nGaAs P/
A structural cross-sectional view of an InP semiconductor laser device is shown.
30 is a p-electrode, and other symbols are the same members as in FIG. 2 with the same symbols.

The p-electrode 30 has a Ti film 31 with a thickness of 500 mm and a Ti film 31 with a thickness of 100 mm.
It has a four-layer structure in which a Ti-Pt mixed film 32 with a thickness of 500, a Pt film 33 with a thickness of 500, and an Au film 34 with a thickness of 3 μm are sequentially laminated. When such an electrode structure is crystallized by heat treatment, since the Ti crystal is hexagonal and the Pt crystal is hexagonal, the crystal grains become smaller and denser, and the gaps through which the ribs pass through are reduced.

The mixing ratio of the Ti--Pt mixed film 32 is desirably 1:1, but even with an unbalanced mixing ratio, it is necessary to have a ratio of 3, that is, the content of Ti or Pt must be 30% or more. Further, in the above example, the thickness of the Ti-Pt mixed film 32 is 1,000 layers, but the appropriate thickness is in the range of 500 to 1,500 layers, and Til*31. Ti-Pt mixed film 32. It is important to keep the total thickness of the three Pt films 33 at a constant value of about 2,000. This is because, as described above, if the thickness is increased, stress will occur, which will have an adverse effect on the light emitting characteristics.

Next, a method for forming the same will be explained. After forming the contact layer 5 by liquid phase epitaxial growth, a Ti film 1 with the above thickness is formed by electron beam evaporation. Ti-Pt mixed film 32. Pt films 33 are sequentially deposited. Next, a membrane with a thickness of 3 .mu.m is applied using a conventional electrolytic plating method, followed by heat treatment at 430.degree. C. for 30 minutes in a hydrogen stream.

Next, an n-electrode 20 with a thickness of 2000 was deposited, and further,
Heat treatment is performed at 380° C. for 1 minute. Finally, the semiconductor laser is completed by folding, but when this was detected by Auger electron spectroscopy, no transmission of Au was observed, and the number of pinholes was less than 10 3 /cnl. Therefore, the electrode configuration according to the present invention is effective.

Although the above example has been explained using a VSB type buried semiconductor laser, it goes without saying that it can also be applied to other BH type or PBH type lasers or light emitting diodes.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, the transmission of the sieve in the electrode is eliminated, and the emission characteristics of the semiconductor laser are maintained at high efficiency, which greatly contributes to improving its reliability. It is something to do.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a conventional semiconductor laser according to an embodiment. In the figure, 1 is an n-1nP substrate, 2 is an n-InP buffer layer, 3 is an n-1nGaAsP active layer, and 4 is a p-1nP
Claso F layer, 5 is p-1nGaAs P contact layer, 6 is p-
InP current blocking layer, 20 is an n electrode 10 is a conventional p electrode (of which 11 is a Ti film, 12 is a
is a Pt film, 13 is an Au film), 30 is a p-electrode according to the present invention (31 is a Ti film, 32 is a Ti-Pt mixed film, 33 is a Pt film, and 34 is an Au film). Figure 1 Figure 2

Claims (2)

[Claims] (1) A semiconductor light emitting device characterized by being provided with a multilayer electrode in which four layers consisting of a Ti film, a Ti-Pt mixed film, a Pt film, and an Au film are sequentially laminated. (2) The four-layer electrode consisting of the Ti film, Ti-Pt mixed film, Pt film, and Au film has p-InGaAsP (0<x<1
, 0<y<1.