JPS6021586A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the variation of element shape by side etching by a method wherein the surface layer of an InGaAsP/InP series multilayer epitaxial crystal is made of InP, and an oxide film is formed thereon and chemically etched. CONSTITUTION:An N type InP layer 6, an InGaAsP active layer 5, a P type InP clad layer 4, an InGaAsP contact layer 3, an InP layer 2, and an InGaAsP cap layer 1 are grown on an InP substrate 7 by a liquid growing method. The cap layer 1 is removed by etching, a phosphorus glass film being formed on the InP layer 2 and made as a mask 8, and being then etched with Br-methanol solution. Then, the side surface is filled with a P type InP layer 9, an N type Inp layer 10, and an InGaAsP layer 11 by liquid phase growth. Since no side etching generates, the width of an active layer can be set at a constant value with good reproducibility. After removal of the oxide film and the InP layer 2, a P-side electrode 12 and an N-side electrode 13 are formed and then the laser diode is completed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a dissimilar welding material using InGaAsP/InP-based materials, and is particularly applicable to long wavelength semiconductor lasers, other long wavelength light emitting diodes, PET, etc. The present invention relates to a compound semiconductor device.

[Background of the invention]

Long wavelength lasers, especially buried hetero lasers, perform mesa etching on multilayer growth layers including the active layer using an oxide film as a mask.
It is necessary to control the active layer width to a width of 1.5 μm. A conventional long wavelength laser is, for example, an n-In laser as shown in FIG.
Multilayer growth layer with 4-layer structure on p substrate
GaAsP, p I”P.

Using InGaAsP, the fourth layer of InGa
An oxide film was formed on the AsP surface, and a mesa structure was formed by chemical etching using this oxide film as a mask (b).

When such an InGaAsP quaternary mixed crystal is used, side etching of the crystal occurs depending on the composition of the mixed crystal as shown in Figure 2. Moreover, this side etching is influenced by the deposition conditions of the oxide film, and the amount of side etching cannot be determined quantitatively. becomes difficult to control. On the other hand, when considering the case where electrodes are formed in a device, a mixed crystal composition with a large amount of As and a large amount of side etching is advantageous in terms of lowering the contact resistance.

In conventional technology, in order to reduce the amount of side etching, it was necessary to use a composition close to InP, which is disadvantageous in terms of contact resistance, so high concentration Zn diffusion technology is required to form electrodes with low contact resistance. Met. 7. Since the diffusion coefficient of n is very large, it is extremely difficult to obtain a shallow diffusion layer with high surface concentration with good reproducibility.

[Purpose of the invention]

The present invention prevents variations in the element shape due to the side etching of the crystal as described above, and can also form ohmic electrodes with low contact resistance at high temperatures even with impurities introduced into the crystal during crystal growth without using diffusion technology. High InGa
An object of the present invention is to provide a semiconductor device formed on Asp or InGaAS mixed crystal.

[Summary of the invention]

The present invention eliminates the above-mentioned problems and provides an InGaAsP/InP-based semiconductor device having good ohmic contact, and forms a multilayer crystal structure as shown in FIG. 3(a). . The feature of the present invention is that during multilayer crystal growth, the first I''GaAap or I
nG a A second InP on 84-element Qr ternary mixed crystal
layer or second layer. The purpose is to provide a third InP and InGaAsP layer. Then, the third InGaAs
PJ- is completely etched off by chemical etching, and the second
A predetermined pattern is formed on the InP# surface using an oxide film as a mask. The third InGaAsP quaternary mixed crystal is
During crystal growth, if the surface layer is InP, this is to prevent the growing surface from becoming mirror-like due to thermal decomposition. is not necessary.

Next, the multilayer crystal is etched using a mask formed on this InP surface layer. In this case, since the surface layer is InP, by selecting an appropriate etching solution, it is possible to form a mesa structure without any side etching. Furthermore, a fourth InGaA layer is added to the area removed by mesa etch.
sP quaternary mixed crystal or 5th. 4th InP + InGaA
A planar structure is formed by forming an sP layer. Finally I n
The oxidation mask on the PJ surface is removed, the InP is selectively etched, and the surface layer of the mesa is covered with a second InGaAsP or I
Confectionery is made by forming an electrode on the nGaAs quaternary or ternary mixed crystal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. This figure shows the process of a buried hetero-type laser. Third
Multilayer growth (6 layers) was performed as shown in Figure (a).

(100) n-type I n P 6 on the InP substrate 7,
InGaAsP active layer 5.1) IfIFF cladding layer 4
．． InGaAsP near:/tact layer 3. The IflP layer 2 and the InGaAsP cap layer 1 were grown by liquid phase growth. In the above growth, the composition of InGaAsP has the same lattice constant as InP, and the emission wavelength is 1.3 pm.
In0.48GaO, ! 12AS0.24P
Similarly, the lattice constant of the I"GaAsp contact layer with the composition of O-76 matches that of InP, and the optical wavelength is ~1.5 μm.
I no, gGao, s+A8o, sPo, corresponding to
The composition of g was used. The uppermost InGaAsP1 layer has the same composition as the active layer I''GaASP5.The cap layer InGaAsP1 on the multilayer growth layer
After removing sP1 by chemical etching, a phosphorus glass film is deposited on the InP layer 2, as shown in FIG. 3(b).
It was formed by the VD method and used as an etching mask. Furthermore, the crystals were etched with f3r-methanol solution and shown in Figure 3 (C
), the side surfaces of the crystal are successively coated with a p-type InP layer 9, an n-type InP layer 10, an I
It was filled with an nGaAsP layer 11 to form the structure shown in FIG. 3(d). In this case, the phosphorus glass film of the mask is deposited on the InP crystal, and no side etching occurs. Therefore, the width of the phosphorus glass film of the mask is kept constant at 6μ, and the width of the active layer can be adjusted with good reproducibility. It was possible to maintain a constant value of 2μ. After the buried growth, the oxide film was removed, the InP layer 2 on the surface was removed, a p-side electrode and an n-side electrode were formed, and a chirality of #) aoo μm was formed by opening to form a laser diode. These corresponding InGa
With the Asp composition, it was possible to easily create a buried hetero laser with a small band gap and a series resistance of 3 to 4 Ω. The above laser has IQ'h as a result of temperature acceleration test.
It was confirmed that it has an average lifespan of r or more.

The above method of forming an electrode that prevents side etching of the InGaAsP quaternary crystal and has low contact resistance includes a buried hetero-type laser having another structure, and
It was confirmed that the present invention is also effective for long wavelength light emitting diodes and light receiving elements of the InGaAsP quaternary crystal system, which have minute light emitting and light receiving areas.

Furthermore, the quaternary composition of I''GaA SP constituting the laser is, of course, 1.0 μm to 1.5 μm.
It is possible to freely select a desired emission wavelength range.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a multilayer grown crystal used in a conventional buried heterostructure laser and a cross-sectional view of a mesa-etched crystal, and Figure 2 is a cross-sectional view of an I n Ga As P44 crystal under an oxide film.
FIG. 3 is a graph showing the relationship between the side etching amount of the original composition crystal, and is a cross-sectional view of the crystal structure and a cross-sectional view of the device when the present invention is applied. In FIG. 3, 1... InGaAsP cap layer, 2... InP mask forming layer, 3... P InGaAsP electrode forming layer,
4... p-InP cladding layer, 5... InGaA,
sP active layer, 6...n-In p buffer layer, 7.
n''-InP substrate, 8... phosphorus glass etching mask, 9... p-InP buried layer, 10... n-I
n p buried layer, 11...InGaA8P buried layer, 1
2°” p-side electrode, 13 ・n 1ltl electrode. fJ i Figure 2 1fJ3 Figure

Claims (1)

[Claims] 1. When forming an oxide film on the surface of an InGaAsP/InP multi-no epitaxial crystal and performing partial chemical etching, the surface layer on which the oxide film is formed is InP,
A compound semiconductor device characterized by forming an oxide film thereon and performing partial chemical etching. 2. When forming the surface layer of the above multilayer crystal into an InP layer, after removing the InGaASP quaternary mixed crystal as the In()aAsPd original mixed crystal as the final growth layer during crystal growth by selective etching, the InP layer as the second layer is removed. 2. The compound semiconductor device according to claim 1, wherein an oxide film is formed on the surface of the semiconductor layer, and then partial chemical etching is performed. 3. The compound semiconductor device according to claim 1, wherein a phosphorous glass (PSG) film is used as the oxide film used in the partial etching.