JPS6047237B2 - Method for manufacturing optical semiconductor devices - Google Patents

Description

[Detailed description of the invention] (1) Technical field of the invention The present invention relates to a liquid phase epitaxial growth method.

In particular, it is used in semiconductor devices for optical communication, etc., and has an indium gallium arsenide (Ino, 5. Gao, O, As) layer in the lower layer and indium phosphide (InP) in the upper layer, and is defect-free and has high performance. This invention relates to improvements in liquid phase epitaxial growth methods for forming quality semiconductor stacks. (2) Background of the technology The liquid phase epitaxial growth method consists of a container in which a temperature program suitable for crystal growth can be arbitrarily set, and a molten liquid (hereinafter referred to as melt) of the substance to be grown, which is provided inside the container.

) Using a device consisting of a slider having a housing opening and a carbon boat having a recess for housing a substrate placed in opposition to the slider, a melt having a desired composition is poured into each of the openings of the slider. The slider is sequentially moved so that the melt contacts the substrate accommodated in the recess provided in the carbon boat, and a layer consisting of each crystal is grown based on a preset temperature program. A method that is particularly effective in that it allows the continuous formation of a laminate consisting of a plurality of layers having similar compositions. On the other hand, since the low-loss wavelength range of optical fibers mainly composed of silica glass (Si00) used for optical communication is the 1 [μm] band, the operating wavelength range is 1 to 2 μm.
There is a demand for semiconductor devices for optical communications, such as light emitting elements and light receiving elements, which are in the [μ] range.

Indium gallium arsenide (In0.53Ga0, O, A
s) is known, and efforts are being made to develop a technique for forming a semiconductor stack in which this semiconductor can be used as an active layer (active layer such as a light emitting layer or a light absorbing layer).

Specifically, indium gallium arsenide (Ino...

Gao, O, As) as the light absorption layer, and indium phosphide (
In order to manufacture an avalanche photodiode with a multiplier layer of InP), indium gallium arsenide
. Efforts are being made to develop technologies for forming defect-free, high-quality laminates of GaO, O, As) and indium phosphide (InP), and for this reason, various methods such as the liquid phase epitaxial growth method described above are being developed. Improvements in semiconductor deposition methods are being pursued. (3) Prior art and problems Using the liquid phase epitaxial growth method, indium gallium arsenide (IrlO.53GaO.47AS) is grown on the (100) plane of a substrate made of indium phosphide (IrlP).
When forming a light absorbing layer made of 100% phosphorus and a multiplier layer made of indium phosphide on top of this, when growing the upper multiplier layer,
The growth solution melts the lower light absorption layer, making it difficult for the upper multiplication layer to deposit (hereinafter referred to as meltback).

). Therefore, in order to avoid this, indium gallium arsenide phosphide (■ n1 -0GaXA
A technique of interposing an S1-, P, ) layer was known.

However, this anti-melt back layer must have two requirements: the lower layer should not melt back during the growth process of the anti-melt back layer itself, and the anti-melt back layer should not melt back as the upper layer grows. Therefore, its composition is subject to relatively severe restrictions, and must be approximately 1.3 [μm] in terms of wavelength, which has been a major bottleneck for industrial use.

Furthermore, even if the composition is appropriately selected, if defects such as sliding scratches and ungrown bits exist in this anti-melt back layer, these defects will be removed when a multiplication layer is grown on the anti-melt back layer. There was a problem that the underlying light absorption layer was melted back due to defects. The thickness of the anti-melt back layer is essentially required to be thick.In fact, if it is too thick, it tends to cause functional problems, so it is formed quite thin, so it is easily penetrated by slight sliding scratches, etc. It is. In order to avoid such disadvantages, once the growth of the anti-melt back layer is completed, the growth is stopped, the wafer surface is observed and the defective area is removed, and then the multiplication layer is grown again. However, in this method, the anti-melt back layer and the multiplication layer are not grown continuously.
There is a disadvantage that the hetero interface is not necessarily good, and furthermore, the process of cutting out the defective parts of one wafer and selecting only the good parts is not easy in terms of process control, and has the disadvantage of poor industrial applicability. Was. As another means to overcome these drawbacks, the applicant of the present patent has developed a (100) plane of indium phosphide (InP) as a substrate.
11) When an indium gallium arsenide (IrlO.53GaO.47AS) layer, which serves as a light absorption layer, and an indium phosphide (InP) layer, which serves as a multiplication layer, are sequentially grown on the A-plane,
It was discovered that it was possible to form a laminate of high quality with no defects without requiring the anti-melt back layer as described above, and filed a patent application ((Patent Application No. 57-05010)
No. 3).

Although this method is quite advanced, it is essential to keep the growth start temperature of indium phosphide (InP), which is the multiplication layer, below 580 [°C], so (a) the growth rate is slow;
(Example) There are several drawbacks such as low carrier concentration, which is difficult to achieve, and further improvements are desired. (4) Purpose of the Invention The purpose of the present invention is to meet this demand, and the purpose of the present invention is to meet this demand by producing indium gallium arsenide (11
An anti-melt back layer is used in the liquid phase epitaxial growth method, which is most suitable for forming a stack consisting of an indium phosphide (InP) layer deposited on a layer (10.53Ga0.47AS), but there are restrictions on the composition of the semiconductor. The growth temperature is relaxed and continuous growth is possible, and the growth temperature can be freely selected.As a result, it is possible to use an industrially efficient growth temperature, which is as low as desired for optical devices. It is an object of the present invention to provide a liquid phase epitaxial growth method which has many advantages such as being able to realize a carrier concentration.

(5) Structure of the Invention The liquid phase epitaxial growth method according to the present invention includes (a) indium gallium arsenide (InO.53GaO.4) on the (111)A plane of a substrate made of indium phosphide (InP);
A layer made of indium gallium arsenide (IrlO.53GaO.47,AS) is formed, and a layer made of indium gallium arsenide phosphide (Inl-XGaxAs
forming an anti-melt back layer consisting of
The indium gallium arsenide phosphide (Inl-XGaxAs
This is achieved by forming a layer made of indium phosphide (InP) on the anti-melt back layer made of -XGaxAsl
The number of anti-melt back layers made of indium gallium arsenide (InO.53Ga
O. The X
This is achieved by making the values progressively smaller and the y values progressively larger.

The inventor of the present invention has developed an indium phosphide (InP) substrate (
111) An indium gallium arsenide (IrlO.53GaO.47AS) layer having a (111) A-plane is formed on the A-plane, and an indium gallium arsenide (IrlO.53GaO.47AS) layer having a (111) A-plane is formed on the A-plane. The reason why the growth starting temperature must be lowered in the liquid phase epitaxial growth method in which the anti-melt back layer is omitted by growing indium gallium arsenide (InO.53GaO.47AS)
) to avoid the meltback of (111)A
We came up with the idea that even when using a surface, the above-mentioned drawbacks could be overcome by using an anti-melt back layer, and in order to put this idea into practice, we developed an indium phosphide (ITlP) substrate (
111) Indium gallium arsenide (InO.53
GaO. 47AS), an anti-melt back layer made of indium gallium arsenide phosphide (Inl- The present invention was completed after experimentally confirming that the condition was good.

In the above configuration, indium gallium arsenide phosphide (I
The anti-melt back layer made of nl-XGaxAs,-,P,
O. 53GaQ. The mixed crystal ratio of indium (In), gallium (Ga), and phosphorus (P) is adjusted so that the band gap becomes smaller from the indium phosphide (Irll) layer, which is the upper layer, from the indium phosphide (Irll) layer, which is the upper layer. .

That is, the closer to the multiplication layer, the larger the mixed crystal ratio of indium (In) and phosphorus (P), and the smaller that of gallium (Ga). In other words, the anti-melt back layer is one layer, and the value of the mixed crystal ratio X in that layer is 0.
It is desirable that the value of y continuously change from O to 1, respectively. However, in the liquid phase epitaxial growth method, such a continuous change in the mixed crystal ratio is not possible, so 0.47>X>0 and 0xy<1
It is advantageous to provide one or more indium gallium arsenide phosphide (Inl-XGaxAsl-YPy) layers having x and y values selected in the range . When the number of anti-melt back layers is plural, the X value thereof is gradually decreased from the layer in contact with the light absorption layer to the layer in contact with the multiplication layer within the above range, and the y value thereof is similarly increased. It goes without saying that this must be done. (6) Embodiments of the Invention A liquid phase epitaxial growth method according to an embodiment of the present invention will be explained below with reference to the drawings, and the structure and unique effects of the present invention will be clarified.

As an example, (111
) Using the A side, indium gallium arsenide (InO.5
3GaO. 47AS) with an operating wavelength of 1.65 [
Indium gallium arsenide phosphorus (InO・76Ga0・24AS0・52yP0
The case where an anti-melt back layer consisting of 48) is interposed will be described. FIG. 1 shows a cross section of a liquid phase epitaxial growth apparatus used in an embodiment of the present invention. In the figure, 1 is a carbon boat having a recess for accommodating a substrate, 2 is made of indium phosphide (InP), and (11
1) A substrate with the A side as the upper surface, and 3) a slider having melts of respective crystals. Further, 4 to 8 are melts used in this example, 4 is a melt back melt, 5 is a buffer layer melt, 6 is a light absorption layer melt, 7 is an anti-melt back layer melt, and 8 is a tamel for the multiplication layer. The composition and saturation temperature of each melt are shown below along with the numbers in FIG.
Since the saturation temperature Ts of each melt is around 650 [°C], each melt is kept in a uniform state by leaving it at 670 [°C] for about 1 hour prior to growth.

Thereafter, when cooling is performed at a cooling rate of 0.7 [°C] per minute, the growth of the first buffer layer starts at 652 [°C], and the growth of the last multiplication layer ends at 639 [°C]. During this time, the slider 3 is successively slid in the direction of arrow A to bring each melt into contact with the substrate 2 for a desired time. FIG. 2 is a cross-sectional view of the laminate realized by the above steps, in which 12 is an indium phosphide (InP) substrate;
15 to 18 represent a buffer layer, a light absorption layer, an anti-melt back layer, and a multiplication layer, respectively, and the thickness of each layer of 15 to 18 is 2.5 [μm], 2 [μm], 1 [μm], respectively.
It is 2 [μm].

As a result of observing the cross section of this laminate by holding the laminate under one's arm, it was confirmed that the heterojunction interface between these layers was extremely flat and no meltback had occurred. Furthermore, the surface condition is good, and it is possible to realize a high-quality laminate without defects. According to the above process, restrictions on the composition of the semiconductor constituting the anti-melt back layer are considerably relaxed compared to those in the prior art, and it is possible to arbitrarily select the growth temperature. Therefore, continuous growth can be achieved in a short period of time, effectively contributing to improving industrial applicability.

(7) Effects of the invention As explained above, according to the present invention, indium gallium arsenide (Indium gallium arsenide) used in semiconductor devices for optical communication, etc.
O. 53GaO. 47AS) layer on the indium ion (
In the liquid phase epitaxial growth method that is most suitable for forming a stack formed by depositing IrlP, an anti-melt pack layer is used, but restrictions on the composition of the semiconductor are relaxed, continuous growth is possible, and The growth temperature can be freely selected5, and as a result, an industrially efficient growth temperature can be used, and a low carrier concentration desirable for optical semiconductor devices can be achieved, among other advantages. It is possible to provide a liquid phase epitaxial growth method having the following methods.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an apparatus used in a liquid phase epitaxial growth method according to an embodiment of the present invention, and FIG.
FIG. 2 is a cross-sectional view of a substrate showing the structure of a laminate realized by this example. 1... Carbon boat, 2, 12... Substrate (InP), 3... Slider, 4...
・Melt for meltback (IrlP), 5, 15...
...Buffer layer melt and buffer layer (InP),
6, 16... Melt for light absorption layer and light absorption layer (I
nO. 53GaO. 47AS), 7, 17...
Melt for anti-melt back layer and anti-melt back layer (InO◆76Ga0●24AS0●52P0●48
) ~ 8, 18... Melt for multiplication layer and multiplication layer (
InP).

Claims (1)

[Claims] 1 A substrate made of indium phosphide (InP) (111
) A light absorption layer made of indium gallium arsenide (InGaAs) lattice-matched to the substrate is formed on the A-plane via a buffer layer, and then the light absorption layer is formed by liquid phase epitaxial growth on the light absorption layer. Lattice-matched indium gallium arsenide phosphide (In_1-xGaxAs_1-y
A method for manufacturing an optical semiconductor device, comprising the steps of forming an anti-melt back layer made of Py) and subsequently forming a multiplication layer made of indium phosphide (InP) on the anti-melt back layer by liquid phase epitaxial growth. .