JPH01141898A - Vapor growth method for iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To form a high-quality epitaxial film at low temp. by using the specified org. compd. of a group III element, and decomposing the gas of the compd. before the gas is introduced onto a substrate crystal in the production of a compd. semiconductor by the vapor growth method using an org. volatile compd. of a group III element and a group V element. CONSTITUTION:The org. volatile compd. of a group III element and a group V element is supplied onto a substrate to grow a III-V compd. semiconductor in the vapor phase. The following constitution is used in the vapor growth. Namely, an org. compd. [e.g., diethylgallium chloride (DEGaCl)] having at least one group III element-halogen element bond is used as the org. volatile compd. of a group III element, and the raw gas 11 of the group III organometal (gaseous H2 12 is used as a carrier) is decomposed in a reaction tube 1 before introduced onto the substrate crystal 3, and then supplied onto the substrate crystal 3. Light irradiation (e.g., a deuterium lamp 9) and/or heating 5 (e.g., resistance heating, IR lamp heating, etc.) are preferably used as the heating source.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for vapor phase growth of ■-V group compound semiconductors, particularly for IV group compound semiconductors that form high-quality epitaxial films at low temperatures. It is related to semiconductor organic metal vapor phase growth technology.

(Prior art) ■-Epitaxially grown layers of group V compound semiconductors are used in optical devices such as light emitting diodes and laser diodes,
It is widely applied to high-speed devices such as ET. Furthermore, recently, in order to improve device performance, a fine structure in which thin film semiconductors of several to several tens of amperes are stacked is required. For example, a laser diode with a quantum well structure can reduce driving current, improve temperature characteristics, and shorten the oscillation wavelength. In addition, F using two-dimensional electron gas
ET and the like are expected to be used as high-speed, low-noise devices.

These thin film epitaxial growth methods include vapor phase epitaxy (VPE) using gas such as metal organic chemical vapor deposition (MOCVD) and halogen transport, and growth using a beam of elements in a high vacuum. The molecular beam epitaxial growth method (MBE method) is widely used. Among these methods, the metal organic chemical vapor deposition method (MOCVD method) is particularly popular as a mass production technology because the equipment is relatively inexpensive and many substrates can be processed at once.
The most anticipated.

By the way, in the MOCVD method, V-hydrogenated compounds such as arsine (AsH3) and phosphine (PH3) are usually used as group V raw materials, but these are highly toxic and dangerous, so strict safety measures must be taken. It is extremely inconvenient to handle.

In addition, in the MOCVD method, the temperature is usually 600"C to 700'C
However, when using a structure in which thin film semiconductors are stacked in a device, interdiffusion of constituent atoms due to heat treatment at high temperatures often becomes a problem. A newly grown fine layer structure may be successively destroyed by thermal diffusion during the growth of the upper layer, and for the same reason it is difficult to obtain a steep impurity profile. More low temperature at least 60
It would be good if it could be grown at temperatures below 0°C, but group V hydride raw materials have a low decomposition rate at low temperatures, and in the case of phosphine in particular, it hardly decomposes at 500'C. For this reason, the supply efficiency of group V atoms becomes low during low-temperature growth, leading to a decrease in the quality of the grown film.

For these reasons, group V organic compounds with lower decomposition temperatures than arsine and phosphine, such as I. ethyl arsine (TEAs) and l. ethyl phosphine (TEP), are preferred.
In recent years, many attempts have been made to use such materials as Group V raw materials. Group V organic compounds are much less toxic and, since they are liquids, do not require high-pressure cylinders, so they are expected to be used as raw materials to replace arsine and phosphine. However, in the case of growth using Group III organic compounds as raw materials, a large amount of carbon is incorporated into the grown film. In normal MOCVD, only the substrate portion is heated, but this is thought to be because the decomposition of the raw material in the boundary layer on the substrate is not complete, so that some of the material reaches the substrate surface undecomposed.

This was improved by the magazine ``Journal of Electronic Materials'' (Journal of El
This is a method using arsenic metal as a group V raw material, as described in Sections 433 to 449 of Electronic Materials) J, Vol. 14, No. 4 (1985).

With this method, there is no problem with the decomposition rate of group V raw materials,
It's also safe. Hydrogen gas is flowed over arsenic metal maintained at 425 to 475" C, and arsenic vapor is transported downstream using this hydrogen as a carrier. In a short low temperature region downstream, trimethyl gallium (TMG), a group II organometallic raw material, is produced.
were mixed and supplied onto the substrate to grow GaAs.

(Problems to be Solved by the Invention) (1) Let us consider the above-mentioned problems of the prior art in the epitaxial growth method of a group V compound semiconductor thin film.

The surface condition of the GaAs thin film obtained by the method using arsenic metal as the Group V raw material is extremely poor and contains many defects. When AsH3 is used instead of arsenic metal in the same device, a mirror surface is obtained, so the problem is clearly caused by the use of arsenic metal. The reason for such a decrease in crystallinity is considered to be as follows.

In the above conventional technology, the temperature of the arsenic metal is 425 to 47 in the piping downstream from the mixing area of group V element vapor and group II organometallic raw material.
The temperature was kept at a moderate temperature, much lower than 5°C.

As a result, arsenic partially precipitates on the tube wall in the downstream low-temperature mixing zone. On the other hand, when trimethyl gallium (TMG) used as a group Ⅰ organic metal raw material is thermally decomposed, it becomes metallic gallium with an extremely low vapor pressure, but the temperature of the above piping is high enough for this decomposition, so trimethyl gallium does not reach the substrate. Some of the metal gallium precipitates out beforehand. Furthermore, since the atmosphere contains arsenic, GaAs nuclei grow in the gas phase. Since these nucleated substances also reach the substrate, there are many defects and the surface condition is extremely poor.
It seems that only an aAs thin film was obtained. The same holds true even when triethyl gallium (TEG) or the like is used.

By the way, according to the above-mentioned conventional technology, the decomposition rate of group Ⅰ organometallic raw materials decreases especially at low temperatures, and since group V elements are used, effects such as the promotion of decomposition by active hydrogen atoms from AsH3 cannot be expected. Carbon pollution from group raw materials increases. Therefore, from this point of view, it is preferable to fully decompose the Group 1 raw material before supplying it onto the substrate.

An object of the present invention is to overcome the drawbacks of the prior art and to provide a IV group compound semiconductor vapor phase growth technique that forms high-quality epitaxial films at low temperatures.

(Means for Solving the Problems) According to the present invention, in the epitaxial growth method of a ■-V group compound semiconductor by supplying an organic volatile compound of a group ■ element and a group V element onto a substrate, Using an organic compound having at least one bond of a group (III) element and a halogen element as the organic volatile compound, decomposing the group (III) organometallic raw material gas before introducing it onto the substrate crystal, and then supplying it onto the substrate crystal. 2) The method of vapor phase growth of group V compound semiconductors is changed.

(Function) Trimethyl gallium (TMG) and triethyl gallium (T E
When using materials such as G), these decompose into metallic gallium, which has an extremely low vapor pressure, and precipitates before reaching the substrate. Furthermore, if the atmosphere contains arsenic, GaAs nuclei will grow in the gas phase.

On the other hand, organic compounds having at least one bond between a group ■ element and a halogen element are used as organometallic raw materials for group ■ elements.
For example, when DEGaCl is used, when this compound is decomposed, only two alkyl groups are eliminated to produce a metal monohalide, that is, GaCl. This G a
CI is approximately 300' C or more, which is commonly used, and 9[+[
It is stable in the gas phase in the growth temperature range up to about 16C and reaches the substrate without precipitation. Furthermore, even if there is arsenic in the atmosphere, unless there is a GaAs substrate with adsorption reaction sites, GaCl"l/4As4"l/282 -+GaAs+
) Since the reaction of IcI does not proceed and the supersaturated state is maintained, no nucleus growth of G'a As in the gas phase or growth on the reaction tube wall occurs.

As described above, if an organic compound having at least one bond between a group III element and a halogen element is used as an organometallic compound of a group III element, it can be prepared in an independently temperature-controlled decomposition region before being supplied onto a substrate crystal. Since the Group (1) source gas can be decomposed in advance, it is possible to realize a vapor phase growth method for Group IV compound semiconductors that forms high-quality epitaxial layers even at low temperatures.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of an apparatus for implementing the present invention. GaAS was grown using this growth apparatus. There is a quartz susceptor 2 in a reaction vessel 1, on which a substrate crystal 3 is placed. A resistance heating or infrared lamp heating device 4.5.6 is provided on the outside of the reaction vessel 1, and the entire reaction vessel 1 is connected to the substrate installation area, the decomposition area upstream thereof, and the As supply where the As metal 7 is placed further upstream. It can be divided into three areas and heated independently. The reaction vessel 1 in the decomposition region has a synthetic quartz window 8 through which light from a deuterium lamp 9 can be introduced. The group (2) organometallic raw material is directly introduced into the decomposition region through a quartz tube 10, and 11 to 14 are other gas introduction systems.

11 is a DEGacl bubbler, and 12 is H2 gas serving as a carrier. Each gas is controlled by a flow rate control device 13.
is introduced into the reaction vessel 1 via the valve 14.

Carrier H2 gas was flowed for 717 min through the As supply area maintained at 400' C, and the substrate installation area was
The decomposition zone was heated to 400-900°C. The decomposition region was irradiated with light from a deuterium lamp 7 as needed. Then the partial pressure D of lXl0-'torr
60 ml of EGaCl was supplied to grow GaAS to a thickness of ~2 μm.

The temperature of the decomposition area and the substrate temperature (substrate installation area) are both 4.
When the temperature is 50°C and no light is irradiated, that is, when the group III source gas is not actively decomposed in advance, the grown film is p.
type conduction, hole concentration is 5 x 10 "C11"
Met. In the photoluminescence spectrum of this sample at 77K, only weak light emission due to carbon acceptors was observed.

On the other hand, the temperature of the decomposition region is 800°C, and the substrate temperature is 4
At 50°C1 and no light irradiation, the hole concentration decreased to 4 x 1016C11-3, although it was p-type. Next, the temperature of the decomposition region and the substrate temperature were both set to 450° C., and light from a deuterium lamp was irradiated. The grown film obtained at this time is still p-type, but the hole concentration is I x 10
``cm-''. Therefore, the temperature of the decomposition region was set to 800°.
As a result of irradiation with light from a deuterium lamp, an n-type crystal with an electron concentration of 3×10"C11-' and a fairly high purity was obtained. As a result of these growths, precipitates were formed on the inner wall of the reaction vessel upstream of the substrate crystal. was not observed, and all of the obtained films had a mirror surface.

As is clear from the above, by using DF and GaCl as group II organic metal raw materials, it is possible to use group V AS metals and decompose the group III raw material gas by heating or light irradiation before supplying it onto the substrate crystal. It has been shown that there is no reduction in supply efficiency or crystallinity due to precipitation or vapor phase nuclear growth during the process, and that the incorporation of force-bonded impurities into the grown film can be reduced by one to two orders of magnitude. Also, the same result is D
It can also be obtained by growing InP using MInCl and P powder. Furthermore, if quartz parts that easily react with AI are replaced with SiC-coated or carbon-made ones, similar results can be obtained with the growth of AlAs using DEAICI and As metal. The present invention can be applied to the growth of group V compound semiconductors. The alkyl group constituting the group (2) organometallic compound may be any other alkyl group, and the easier it is to decompose and eliminate, the better. The light source used for light irradiation may be an excimer laser, and when a carbon tube is used as the reaction vessel, high frequency waves may be used as the heating means.

(Effects of the Invention) As described above, according to the present invention, the group (III) raw material gas is decomposed in a decomposition region whose temperature is independently controlled or irradiated with light, and then supplied onto the substrate crystal. Forms high-quality epitaxial films even at low temperatures.
-A group V compound semiconductor vapor phase growth method was realized, and the effects of the invention were demonstrated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an apparatus for carrying out the method of the present invention. 1-reaction vessel, 2-quartz susceptor, 3-substrate crystal, 4.
5.6-Resistive or infrared lamp heating device, 7-As metal, 8-Synthetic quartz window, 9-Deuterium lamp, 10-
Group quartz introduction tube, 1l-DEGaC1 bubbler, 12-carrier H2 gas, 13-flow control device, 14-valve.

Claims (2)

[Claims] (1) In the vapor phase growth method of a III-V compound semiconductor, which is grown by supplying an organic volatile compound of a group III element and a group V element onto a substrate, the organic volatile compound of a group III element is Using an organic compound having at least one bond between an element and a halogen element, the above III.
The group organometallic raw material gas is decomposed before being introduced onto the substrate crystal, and then supplied onto the substrate crystal.
A method for vapor phase growth of III-V compound semiconductors. (2) The method for vapor phase growth of a III-V compound semiconductor according to claim 1, wherein the means for decomposing is light irradiation, heating, or both.