JPH034517A - Vapor growth method - Google Patents

Abstract

PURPOSE:To reduce both quantity of consumption of a virulently positions V hydrogen compound and the quantity of deposition of a harmful V oxide and group V element, and to make it possible to grow a crystal of very high quality by a method wherein a V/III ratio is made very small, and the utilization efficiency of the group V element is enhanced. CONSTITUTION:A P-type AlGaAs layer 102 and an N-type AlGaAs layer 103 are laminated and epitaxially growth on a P-type GaAs substrate 101. Concretely, in an AlGaAs organic metal vapor growth method. A V/III ratio region, wherein a mirror surface is grown between a first V/III ratio region, where non-mirror surface growth is generated at the ratio of V-group element supply quantity and III-group element supply quantity, namely, V/III ratio which is smaller than ratio I and also containing an alkyl compound having a methyl radical as raw material of III group organic metal, and a second V/III ratio region generating a non-mirror surface growth at the V/III ratio larger than ratio 1, is provided, and an epitaxial growth is conducted. As a result, crystal can be grown under a condition wherein the surface morphology is formed into a perfect mirror surface, and high density carbon can also be added.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to an organic metal vapor phase growth method for ■-v group compound semiconductors, and particularly relates to a ■-v group compound semiconductor containing a high concentration of p-type impurities. This invention relates to metal-organic vapor phase growth methods for group compound semiconductors.

(Conventional technology) In the conventional organometallic vapor phase epitaxy method, group V element raw materials and ■
If the supply ratio of group element raw materials (hereinafter referred to as the V/III ratio) is reduced, the surface morphology deteriorates and the growth rate decreases at the same time, so it is normal to set the V/III ratio to be sufficiently larger than the surface morphology deterioration. Met. For this reason, the amount of V hydrogen hydride supplied was larger than the amount of metal supplied, and its utilization efficiency was extremely poor. In order to increase the utilization efficiency of the V-hydrogenide, there has been a method of thermally decomposing the V-hydrogenide. This method was not practical as it was not possible to epitaxially grow a high quality ■-v group compound semiconductor.

Further, as the p-type impurity of the ■-v group compound semiconductor, zinc (hereinafter referred to as Zn), magnesium (hereinafter referred to as Mg), and beryllium (hereinafter referred to as Be) are generally used. - Among these, Zn and Mg have large vapor pressures and diffusion coefficients, and it has been difficult to add them at high concentrations with good controllability and a steep concentration profile. In addition, Be is highly toxic and difficult to handle using organometallic vapor phase epitaxy. It has been known that in conventional organometallic vapor phase epitaxy, as the V/III ratio is decreased, the amount of carbon incorporated increases and the p-type carrier concentration increases. However, when the V/■ ratio is reduced, the surface morphology deteriorates, making it impossible to add carbon at a high concentration to a good quality epitaxial layer. In recent years, a chemical beam epitaxial method has been developed in which epitaxial crystal growth is performed using a beam of group V atoms or molecules obtained by thermally decomposing an alkylated compound of a group Ⅰ element, a group V molecular element, or a hydride of a group V element under high vacuum. Addition of carbon is now possible. However, in this method, the crystal growth equipment is extremely complicated and expensive, and maintaining the vacuum level inside the equipment requires a great deal of labor and expense, making it impractical.

In recent years, attempts have been made to add carbon as a p-type impurity using alkylated compounds of group V elements in metallurgical vapor phase epitaxy. However, in this case, a crystal with good surface morphology could not be obtained, making it impractical.

(Problems to be Solved by the Invention) As mentioned above, the organometallic vapor phase epitaxy method has a problem in that the utilization efficiency of group V source gas is poor. For this reason, a great deal of expense is required to render harmless the cleaning gas after vapor phase growth, which contains a large amount of group (I) hydrides that are harmful to the human body.

Furthermore, if you try to add a high concentration of p-type impurity without diffusion, you will have to use extremely toxic Be, which is impractical, or you will have to use chemical beam epitaxial method, which requires equipment that is expensive and difficult to maintain, or impractical. There is a problem in that when alkylated compounds of group elements are used, good crystal growth cannot be achieved.

The present invention has been made in consideration of the above-mentioned problems, and its purpose is to suppress the amount of Group V raw material gas used and to create a practical gas phase in which it is possible to add carbon at a high concentration as a p-type impurity. The purpose is to present a method of growth.

[Structure of the Invention (Means for Solving the Problems) Conventionally, in organometallic vapor phase epitaxy, if there is a growth condition where the V/III ratio is small and the surface morphology deteriorates, the V/III
It was thought that the smaller the ratio, the worse the surface morphology. However, as a result of extensive research, we have found that when the organometallic contains a methyl group, there are local crystal growth conditions that allow perfect mirror crystal growth under growth conditions where the surface morphology with a small V/III ratio deteriorates. I found it. The vapor phase growth method of the present invention performs vapor phase growth under limited conditions where the V/Iff ratio is small. V/I
Since crystal growth is carried out under conditions where the II ratio is extremely small, gallium hysterol and aluminum gallium hysterol V
(AI Ga As: O<X<1)
1-x, carbon can be added at an extremely high concentration.

That is, in the organometallic vapor phase growth method of gallium hisso and aluminum gallium hisso, an alkylated product having a methyl group is included as a raw material for the group (III) organometal, and the ratio of the supply amount of the group V element to the supply amount of the group (■) (V/III ratio) ) is the first V that produces non-specular growth with a V/III ratio smaller than 1
Epitaxial growth is performed in the crotch region in the V/III ratio region where mirror growth occurs between the /III ratio region and the second ■/■ ratio region where non-specular growth occurs at a V/III ratio greater than 1. be.

(Function) According to the present invention, since crystal growth is performed under conditions where the V/III ratio is extremely small, the utilization efficiency of group V hydrides is extremely high. In addition, since crystal growth is performed under conditions where the surface morphology becomes completely mirror-like, extremely high-quality crystals can be produced.

Since crystal growth is carried out under extremely small V/III ratio conditions, aluminum gallium
As: 0<X<1) as growth x l-
x It is possible to add carbon at an extremely high concentration. Since carbon has a small diffusion coefficient and a high activation rate, pm impurities can be added at a high concentration with excellent controllability, and an extremely steep carrier concentration profile can be formed.

(Example) <Example 1> The details of the present invention will be explained below by taking the growth of gallium ash (GaAs) as an example.

The feedstocks are trimethyl gallium (TMG) and arsine (
As Ha). The growth temperature is 620℃,
The gas flow rate was set to 60 cm/win or more. The supply amounts of arsine, a group V raw material, and trimethylgallium, a group II raw material, are 4 X 10-6a+ol/sin ~ 85 XIOmol/III1n, and 3 X 10-6*ol/, respectively.
IIIln~1.8 x 10-5io1/III1
n, and the V/III ratio was between 0.5 and 4. When the value was less than 0.5, gallium metal was precipitated on the surface of the grown gallium histo. 4 or more, the surface morphology of the grown gallium histo deteriorated. The growth rate at this time was 1 ua+/hr to 5 um/sin.

The conductivity type of the grown gallium histo is all p-type, and V/
The smaller the III ratio, the higher the carrier concentration. The p-type carrier concentration was determined to be 1×101 by van der Barra method.
It became 9 cm ~ 1 x 1020 cIn-3. At this time, the impurity 3 concentration is 5econdary ion Mass 5pe
As measured by ctroietry method, Garbon (
C) The concentration and carrier concentration were almost the same. At this time, the change in lattice constant was 0.02% or less, which was 115 or less compared to the case where the same amount of carriers were generated by adding Be.

When carbon profile analysis was performed, the analytical sensitivity (1017cm-3
) and below the resolution (300 angstroms). When the feedstock VlTri ratio was above 10, the surface morphology became good again. However, at this time, many hillocks were recognized (from tens of thousands of cI11-2 to several hundred thousand (
2)-2). When the film was grown under the conditions of the present invention where the V/III ratio was small and mirror growth was achieved, almost no hillocks were observed. (10,000 cI11-2 or less).

When triethyl gallium (T E G) is used instead of trimethyl gallium as the group material, the V/■ ratio becomes 4.
When the temperature was lower than that, gallium metal suddenly precipitated on the grown gallium histo.

<Example 2> A second example of the present invention will be described below by taking the growth of aluminum gallium histo (AIIGaAs) as an example.

The feedstocks are trimethylaluminum (GMA), trimethylgallium and arsine. Growth temperature is 560-6
The temperature was 20° C., and the gas flow rate was 60011/1n or more. The supply amounts of arsine, which is a group V raw material, and trimethylaluminum, tri, and methylgallium, which are group II raw materials, are respectively I
10-6mol/Sonoori n~4×5 10mol/IIIin% IXI 0-6
a+ol/l1in ~4X5 10 mol/IIIin, 3 X 10-6m
ol/sin −1,8×1 O−511 ol/1n, and the V/III ratio was between 0.8 and 2.

If it is less than 0.8, the surface morphology of the grown aluminum gallium gallium oxide deteriorates, and group Ⅰ metals precipitate. V/I
When the II ratio was 2 or higher, the surface morphology of the grown gallium histopathology deteriorated. Growth rate of epitaxial layer is 1uI
l/hr~5um/IIIin. The conductivity type of the grown gallium hisso was all p-type, and the smaller the V/III ratio, the higher the carrier concentration. The p-type carrier concentration was determined as I x 1019 cm-3 by the van der Para method.
It became ~5 x 1020 cm-3. At this time, the impurity concentration is set to 5econdary Jon Mass Spect.
When measured by the rometry method, the carbon concentration and carrier concentration were almost the same. Same V/III
Under the ratio, the higher the aluminum composition, the higher the carbon concentration and carrier concentration. Carbon profile analysis was conducted in 9-3, and analysis sensitivity (10'c
There was a sharp change below the resolution (300 angstroms) down to below m-3). When the feedstock V/III ratio was above 10, the surface morphology became good again. However, at this time, a large number of hillocks were observed (± tens of thousands of blades to several tens of blades al-2). When the film was grown under the conditions of mirror growth with a small V/III ratio according to the present invention, almost no hillocks were observed (10,000 marks -2 or less).

<Example 3> Figure 1 shows a p-n fabricated using the first example of the present invention.
This is an example of manufacturing a crystal with a junction.

A p-type aluminum gallium histolayer (p-2 x 1019 cm-3) 1 is formed on a p-type gallium histo(100) substrate 101 using trimethylgallium, trimethylaluminum, and arsine by the vapor phase growth method of the second embodiment of the present invention.
02.9000 angstroms were formed. On top of that, an n-type aluminum gallium layer (n=IX1018am-3) 103.35
00 angstroms were formed. FIG. 2 is a carrier concentration profile of the crystal having the pn junction. p
The carrier concentration change at the −n junction surface is below the resolution (10
0 angstrom) or less. Mg or Zn is added to the p-type aluminum gallium histolayer 102 to generate p-type carriers, and a p-
When a crystal having an n-junction was fabricated, the carrier concentration change at the p-n junction interface required more than 200 angstroms. This is because in the embodiment of the present invention, the diffusion coefficient of carbon is small, so the p-n junction position is At Ga A
s/At Ga As: x l-x
y 1-y (0<x, y<1; x-y)
This is because it almost coincides with the heterojunction interface.

In this embodiment, trimethyl gallium and trimethyl aluminum were used to grow the p-type aluminum gallium histolayer 102, but a combination of trimethyl gallium and triethyl aluminum, or a combination of triethyl gallium and trimethyl aluminum may also be used. In any case, including the embodiments of the present invention, in order to generate n-type carriers with good controllability by adding impurities in order to obtain good surface morphology, the V
It is necessary to perform crystal growth under the /III ratio.

In this example, AI Ga As/At.

x1-xGaAs: (0<XTy<1;
x-y) Het-y We took the p-n junction at the mouth junction interface as an example, but G a A
s/G a As homozygous interface, AlGaAs
/AIGaAs homojunction interface can also form a pn junction in the same manner as in this embodiment. Furthermore, it is clear that the present invention can be applied to the growth and formation of a p-type compound semiconductor film containing at least one of gallium and aluminum as a group II element and As as a group V element.

Furthermore, the vapor phase growth method of the present invention can be applied to all p-type layers, such as the p-base layer of hetero-bipolar transistors, the p-type cladding layer and p-type contact layer of laser diodes, and the p-type layer of photodiodes. It is.

[Effect of the invention] As described above, according to the vapor phase growth method of the present invention, V/I
The II ratio was extremely small, and the utilization efficiency of group Ⅰ elements was extremely high. Therefore, the amount of highly toxic V-hydrogenide used was small, and the amount of harmful group V oxides and group V elements precipitated was small. Therefore, the processing costs for group V elements and their compounds can be significantly reduced. Furthermore, extremely high quality crystals were grown at this time.

In AI Ga As (0<x<1), x
l-x Carbon could be added at a high concentration. The activation rate of carbon was extremely close to 1, and p-type carriers could be added at a high concentration without impairing the quality of the crystal. Moreover, the change in lattice constant was also small. Furthermore, carbon has a small diffusion coefficient and an extremely steep carrier concentration profile was obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a crystal including a pn junction according to the present invention. FIG. 2 is an explanatory diagram illustrating the steepness of the pn junction in the embodiment of the present invention. 101...p-type gallium histo(100) substrate, 102
...p-type aluminum gallium histolayer, 103...
N-type aluminum gallium histolayer.

Claims (2)

[Claims] (1) In the organometallic vapor phase growth method for gallium histo- or aluminum gallium histo, the ratio of the supply amount of group V elements to the supply amount of group III elements (V/III ratio) between a first V/III ratio region that causes non-specular growth at a V/III smaller than 1 and a second V/III ratio region that causes non-specular growth at a V/III ratio greater than 1. , where mirror growth occurs at V/
A vapor phase growth method characterized by performing epitaxial growth in a III ratio region. (2) the hydride of the Group V element is arsine;
2. The vapor phase growth method according to claim 1, wherein the alkylated group III element comprises at least one of trimethylgallium and trimethylaluminum.