JPH0613323A - Vapor phase epitaxy method for compound semiconductor mixed crystal - Google Patents

Abstract

PURPOSE:To remove a layer containing an undesired composition to be grown in the case of switching growing gas by etching a grown layer containing previous composition in the case of switching the growing gas by vapor etching, removing the layer containing the undesired composition and then vapor growing a layer containing a different composition. CONSTITUTION:After an InGaAsP layer is grown, supplies of AsH3, PH3 from gas introduction tube 4 are stopped, switched to HCl gas, and the supply of HCl from a gas introduction tube 3 to a material port 6 is stopped. An InGaAsP layer on a surface of a substrate is etched about 2mum by vapor etching. In the case of switching from the AsH3, the PH3 of the tube 4 to the HCl, a flow rate of the HCl from the tube 2 is varied to that necessary in the case of vapor growing a next InP layer. After the substrate is etched by supplying the HCl from the tube 4, the supply of the HCl from the tube 4 is stopped, and switched to PH3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase epitaxial growth method for compound semiconductors, and more particularly to a technique effective when used for forming a multilayer heterojunction structure.

[0002]

2. Description of the Related Art In optical devices such as semiconductor lasers, light emitting diodes, and photodiodes, for example, InGaAs is used.
Heterojunction structures such as P / InP have been used.
A vapor phase growth method is used to form this type of heterojunction structure. Conventionally, InGaAsP, InP, etc. III
The vapor phase epitaxial growth of the group-V compound semiconductor on the substrate is performed by the hydride VPE method using a vapor phase growth apparatus as shown in FIG. 1, for example.

That is, this vapor phase growth apparatus comprises a cylindrical reaction tube 1 made of quartz and an electric furnace 10 arranged around it, and the electric furnace 10 has an axial temperature distribution of the reaction tube 1. It is configured to be able to control. Then, in the reaction tube 1, raw material boats 5 and 6 containing indium and gallium as material sources are arranged on the upstream side (left side in the figure),
A susceptor 8 holding a GaAs substrate 7 for vapor phase growth is arranged on the downstream side. On the other hand, at the upstream end of the reaction tube 1, a first gas introduction tube 2 for supplying gas to the raw material boat 5 is provided.
And a second gas introducing pipe 3 for supplying gas to the raw material boat 6 and a third gas introducing pipe 4 for bypassing the raw material boat and supplying gas to the upstream side of the substrate 7. There is. In addition, 9 is a gas exhaust pipe.

[0004]

By the way, when the multilayer heterojunction structure is formed by the vapor phase epitaxy method, the state in the growth chamber becomes unstable immediately after the composition of the growth gas is switched, so that the composition change is sharp and It was difficult to obtain a good growth interface. Therefore, it has been proposed to provide a growth apparatus with a chamber for waiting the substrate, to provide a plurality of growth chambers, or to attach a slide type cover to the substrate holder. However, when these measures are taken, the growth apparatus becomes complicated, and each has a mechanical operation part, so a seal is required, and it is difficult to completely prevent gas leakage at the seal part. There was also a safety issue.

The present invention has been made in view of the above problems, and it is possible to obtain a heterojunction structure having a sharp composition change and a good growth interface without complicating a growth apparatus. It is to provide a vapor growth method that can be performed.

[0006]

In order to achieve the above object, the present invention provides a method of continuously growing a compound gas having different compositions by vapor phase growth. The growth layer is etched by vapor phase etching to remove a layer having an undesired composition, and then a layer having a different composition is vapor phase grown.

[0007]

In vapor phase growth, when two or more compound semiconductor layers having different compositions are continuously vapor phase grown, the gas composition in the growth chamber becomes temporarily unstable when the growth gas is switched. However, according to the above-mentioned means, a layer having an undesired composition is removed by vapor phase etching, so that the heterojunction structure having a sharp growth in composition change and a good growth interface only by controlling gas switching. Can be obtained.

[0008]

EXAMPLE An example in which the present invention is applied to vapor phase growth of an InGaAsP / InP heterojunction structure by the hydride VPE method will be described below. First, the InP single crystal substrate is placed on the susceptor 8 of the growth apparatus as shown in FIG. In addition, In (indium) is placed in the raw material boat 5 and Ga (gallium) is placed in the raw material boat 6 and installed in the upstream side of the reaction tube. Hydrogen gas was supplied from the gas introduction pipes 2 and 3 at a flow rate of 1000 cc / min, and PH ₃ (phosphine) and AsH ₃ (arsine) diluted to 10% with hydrogen were introduced from the gas introduction pipe 4 to 200 times, respectively.
The substrate temperature was raised to 650 ° C. while being supplied at flow rates of cc / min and 100 cc / min. At the same time, the metal raw materials in the raw material boats 5 and 6 were heated to 800 ° C.

After the temperature became stable, HCl gas was supplied from the gas introduction pipes 2 and 3 at flow rates of 30 cc / min and 5 cc / min, respectively, and the InGaAsP layer was grown to a thickness of 15 μm over 30 minutes. After that, gas introduction pipe 4
The supply of AsH ₃ and PH ₃ from the reactor is stopped to switch to HCl gas, and H from the gas introduction pipe 3 to the raw material boat 6
The supply of Cl gas was stopped (timing T1 in FIG. 2). HCl gas from the gas introducing tube 4 was supplied at a flow rate of 10 cc / min for 30 seconds to vapor-etch the InGaAsP layer on the substrate surface by about 2 μm. AsH of the gas introduction pipe 4
₃ , when switching from PH ₃ to HCl gas, gas introduction pipe 2
The flow rate of HCl gas (30 cc / min) from
Flow rate required for vapor phase growth of nP layer (100 cc
/ Min).

After etching the substrate by supplying the HCl gas from the gas introducing pipe 4, the supply of the HCl gas from the gas introducing pipe 4 is stopped and the pH is switched to PH ₃ (timing T).
2). PH ₃ has a flow rate of 500 cc / min, which is 1
The InP layer was grown to a thickness of 10 μm by flowing for 0 minutes. The composition of the obtained epitaxial layer was analyzed.
As a result, the composition profile was as shown in FIG. 3, and the thickness of the transition layer transitioning from the InGaAsP layer to the InP layer was 0.3 μm.

(Comparative Example) The etching process between the timings T1 and T2 shown in FIG. 2 is omitted, and at the timing T1, the supply of the HCl gas from the gas introducing pipe 3 to the raw material boat 6 is stopped and the gas is supplied. The supply gas from the introduction tube 4 is switched to only AsH ₃ and PH ₃ to PH ₃ , and a 15 μm thick InGaAsP layer is grown on the InP single crystal substrate, and a 10 μm thick InP layer is vapor-phase grown thereon. Let The growth conditions (substrate temperature, raw material boat portion temperature, growth gas flow rate) of each epitaxial layer were the same as those in the above-mentioned examples. When the composition of the obtained epitaxial layer was analyzed, the composition profile was as shown in FIG.
The thickness of the transition layer transitioning from the InGaAsP layer to the InP layer was 1.5 μm.

In the above embodiment, InGaAsP /
Although the growth of InP has been described as an example, the present invention is not limited thereto and can be generally applied to the formation of a heterojunction structure in which mixed crystals of other III-V group compound semiconductors or II-VI group compound semiconductors are laminated. . Further, in the embodiment, the hydride VPE method is used as the vapor phase growth method, but it can also be used when other vapor phase growth methods are used. The etching gas in that case is not limited to HCl, and any gas may be used as long as it has an etching action.

[0013]

As described above, according to the present invention, when two or more compound semiconductor layers having different compositions are continuously vapor-phase grown, the growth layer having the previous composition is vapor-phase etched when the growth gas is switched. Since the layer with an undesired composition is removed by etching with the above method and the layer with a different composition is vapor-grown, the layer with an undesired composition that grows when the growth gas is switched is removed. There is an effect that a heterojunction structure having a sharp composition change and a good growth interface can be obtained without complicating the growth apparatus only by controlling gas switching.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a vapor phase growth apparatus used in an embodiment of the present invention.

FIG. 2 is a time chart showing gas control timing in one embodiment of the present invention.

FIG. 3 is a composition profile showing a composition analysis result of a vapor phase growth layer obtained by applying one example of the present invention.

FIG. 4 is a composition profile showing a result of composition analysis of a vapor phase growth layer obtained by a conventional method.

[Explanation of symbols]

 1 reaction tube 2,3,4 gas introduction tube 5,6 raw material boat 7 growth substrate 8 susceptor

Claims (1)

[Claims] 1. When continuously vapor-depositing two or more compound semiconductor layers having different compositions, the growth layer having the previous composition is etched by vapor-phase etching when the growth gas is switched, and an undesired composition is obtained. The method for vapor phase growth of compound semiconductor mixed crystal, characterized in that the layers of different composition are removed, and then layers of different compositions are vapor-phase grown.