JP2000277444A - Liquid-phase epitaxial growth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize epitaxial growth without decreasing its speed even with a low dislocation substrate, at epitaxial growth of a III-V compound semiconductor. SOLUTION: To allow liquid-phase epitaxial growth by a temperature- difference method or an annealing method on a substrate S of a III-V compound semiconductor such as GaP or InP. Such a substrate S as having dislocation density 104 cm-2 or less is used. Related to the substrate S, an angle θ formed between the substrate surfaced and a crystallographic main surface is 1-8 deg.. The step part of the main surface on the substrate surface is a starting point for crystal growth, improving the growth speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase epitaxial growth method of a III-V group compound semiconductor such as GaP or InP using a low dislocation substrate.

[0002]

2. Description of the Related Art Group III-V compound semiconductors such as GaP and InP are materials mainly used for optical devices such as light emitting diodes, photodiodes and laser diodes. These devices include GaP, InP, etc.
It has a laminated structure in which an n-type semiconductor, a p-type semiconductor, a semi-insulating semiconductor, or the like, to which a small amount of an appropriate impurity such as S or Zn is added, is epitaxially grown on a III-V compound semiconductor substrate.

Conventionally, III-V group compound semiconductors have been
The substrate is manufactured by epitaxial growth using a substrate of a single crystal of a compound such as P or InP. The substrate has a crystallographic main surface, that is, a dense array of atoms, for example, a (111) plane or a (100) plane. It is made to become.

In order to improve the performance of these optical devices, it is effective to suppress defects such as dislocations. Attempts have been made to epitaxially grow a low dislocation substrate having a dislocation density of 10 ⁴ cm ⁻² or less. I have.

[0005]

SUMMARY OF THE INVENTION However, dislocation density
Degree 10^Fourcm^-2Growth using conventional substrates that are super
The speed is controlled by a growth method such as a cooling method or a temperature difference method.
Although different, the typical growth rate is 1 μm in the temperature difference method.
/ Min, while the dislocation density is 10^Fourcm ^-2Less than
When a low dislocation substrate is used, it is about 0.6 μm / min.
Become. Slow growth rate when using low dislocation substrates
The reason is that one of the nucleation sites,
This is presumed to be due to extremely few position defects. Low growth rate
Below, the lengthening of the epitaxial growth process causes
The manufacturing cost increases.

The present invention has been made in view of the above problems, and provides an epitaxial growth method capable of realizing a good epitaxial growth rate even when a low dislocation substrate is used in epitaxial growth of a group III-V compound semiconductor. Things.

[0007]

According to the present invention, there is provided a liquid phase epitaxial growth method for epitaxially growing a substrate made of a III-V group compound semiconductor such as GaP or InP, wherein the substrate has a dislocation density of 10 ⁴ cm. ⁻² or less, and the angle between the substrate surface and the crystallographic main surface is 1 to 8 degrees.

According to the liquid phase epitaxial growth method of the present invention, as shown in FIG. 1, the surface of the substrate S is inclined by θ degrees with respect to the main surface constituting the dense array of atoms. A step occurs in the atomic arrangement on the main surface, and this step serves as a starting point for crystal growth. For this reason,
Even when the dislocation density of the substrate is as low as 10 ⁴ cm ⁻² or less, epitaxial growth occurs quickly. At this time, if the angle θ between the substrate surface and the main surface is less than 1 degree, the step portion becomes too small, and the effect of improving the growth rate is also reduced.
If the temperature exceeds the limit, abnormal growth occurs, and the surface of the grown film becomes uneven. For this reason, the lower limit of θ is set to 1 degree, preferably 2 degrees, while the upper limit of θ is set to 8 degrees, preferably 6 degrees. Usually, the (111) plane or the (1) plane is
00) The plane is selected.

[0009]

Hereinafter, the present invention will be described with reference to Examples.
The present invention is, of course, not limited to such examples, and the liquid phase epitaxial growth method is not limited to the temperature difference method described in the examples, but may be a slow cooling method.

FIG. 2 is a cross-sectional explanatory view of a substrate growth vessel 1 in which liquid phase epitaxial growth is performed by a temperature difference method in the embodiment, wherein a bottom plate portion 2 on which a substrate S is installed and a cylindrical shape provided thereon are provided. It is composed of a portion 3 and a cover plate portion 4 attached to an upper opening of the tubular portion 3, and these are formed of carbon. The substrate growth vessel 1 is placed in a heating furnace having a multi-stage heater in which a temperature distribution is formed in a vertical direction, and is heated so as to give a predetermined temperature distribution in a vertical direction. In this embodiment, the substrate growth vessel 1 contains a melt (melt) 5 containing Ga as a main component, on which GaP is placed.
(50% Ga-50% P) polycrystalline pieces (source material) 6
Is supplied, and a non-doped layer on which no impurity is intentionally added is formed on the substrate S.

[0011] First, GaP substrate (conventional substrate) dislocation density conventionally used in general is a ⁴ × 10 4 cm ^-2, and a low dislocation GaP substrate dislocation density is 2 × 10 ³ cm ^-2 Using a (low dislocation substrate), a GaP non-doped layer was subjected to liquid phase epitaxial growth by a temperature difference method. In this case, the substrate surface is substantially parallel to the (111) plane ((111) ± 0.2
Degree). In the case of a GaP substrate, (11
1) The plane means a plane having P atoms on the surface, and this plane is defined as the substrate surface side. The growth conditions are as follows: the temperature of the melt is controlled to 874 ° C. by controlling the temperature of the multi-stage heater;
The temperature was adjusted to 50 ° C. This growth condition is a typical condition in the temperature difference method. The substrate size was 20 mm square, and the number of samples was 5 for each.

The growth was stopped after a lapse of a predetermined time from the start of the liquid phase epitaxial growth, the thickness of the grown film was measured, and the growth rate was obtained. As a result, the growth rate under typical growth conditions was 1 μm / min for the conventional substrate, but 0.5 to 0.7 μm / min (0.6 μm / min on average) for the low dislocation substrate. Was.

Next, various low dislocation substrates (dislocation density 2 ×) in which the angle (off angle) between the substrate surface and the main surface (111) plane is turned off in the (110) direction within the range of 1 to 10 degrees. 10 ³
cm ⁻² ) were prepared at five points each, and epitaxial growth was performed using this low dislocation substrate under the same growth conditions as described above. The result is shown in FIG. The data in FIG. 3 shows the average value of each sample and its variation range.

FIG. 3 shows that the off angle from the (111) plane is 1
By setting the growth rate to not less than 80 ° C., a good growth rate of 80% or more with respect to the conventional growth rate can be realized. It can be seen that it can be realized. However, when the off angle exceeds 8 degrees, abnormal growth starts to occur in each part, irregularities appear on the surface of the grown film, and when the off angle is 10 degrees, the film thickness uniformity and surface morphology are further deteriorated, and the average film When the thickness is grown to 100 μm, the depth is 40 to 60 μm
Grooves appeared on the surface. The occurrence of such grooves significantly lowers the yield in device manufacturing. From this, it was confirmed that the off-angle of the low dislocation substrate whose surface morphology was healthy and whose growth rate was at the mass production level was 1 to 8 degrees.

[0015]

According to the liquid phase epitaxial growth method of the present invention, the surface of a substrate made of a III-V group compound semiconductor such as GaP or InP is shifted by 1 to the crystallographic main surface.
Since an angle of about 8 degrees is formed, a good crystal growth rate can be realized even when a low dislocation substrate having a dislocation density of 10 ⁴ cm ⁻² or less is used as the substrate, and the surface state is sound. Epitaxial growth can be realized and the productivity is excellent.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a crystal surface portion when a surface of a substrate is inclined by θ from a crystallographic main surface.

FIG. 2 is a schematic cross-sectional view of a substrate growth container used in an example.

FIG. 3 is a graph showing a relationship between an off-angle of a low dislocation substrate and a growth rate ratio to a growth rate when a conventional substrate is used in an example.

[Explanation of symbols]

 1 Substrate growth vessel S Substrate

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Claims (1)

[Claims] 1. A liquid phase epitaxial growth method for epitaxial growth on a substrate made of a III-V group compound semiconductor such as GaP or InP, wherein the substrate has a dislocation density of 10 ⁴ cm ⁻² or less, Liquid phase epitaxial growth method wherein the angle between the main surface and the main surface is 1 to 8 degrees.