JPS61275195A - Method and device for forming compound semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain the titled thin film with less lattice defects and impurities by introducing a hydride contg. an H2 carrier gas and a trace of a group V or VI element over a substrate and alternately introducing specified org. metallic compd. and hydride. CONSTITUTION:A substrate 1 is set on a substrate supporting stand 4 in a reaction vessel 3 and heated by a heating device 5. Then a hydride which is diluted to the first concn. wherein a group III-V compd. or a group III-II compd. is not formed by the reaction with an organometlalic compd. and which contains a group-V or a group-VI metal and an H2 carrier gas are always introduced into the reaction vessel 3 through a pipeline 6 by regulating valves V1 and V2. The hydride diluted with H2 to the second concn. which is higher than the first concn. and the organometallic compd. which is diluted with H2 and contains a group-III or a group-II element are laternately introduced by operating valves V3-8 at regular intervals of time set by a controller 7 and thermal decomposition is carried out to form a group III-V or a group II-VI compd. semiconductor crystal thin film on the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the formation of a ■-V group compound semiconductor thin film and a II-VI group compound semiconductor thin film.

E Summary of Disclosure 1 The present invention involves constantly flowing a trace amount of a hydride containing a group V or group II element together with a hydrogen carrier gas onto a heated substrate in the formation of a semiconductor thin film of a group ■-V or group II-VI compound. While heating, the hydride diluted to a slightly high concentration with hydrogen and the organometallic compound containing a group Ⅰ or group Ⅰ element diluted with hydrogen are alternately poured onto the substrate.

Monoatomic layers of group V or group Ⅰ elements and monoatomic layers of group Ⅰ or group Ⅰ elements are alternately formed on a substrate.

By forming a thin film of ■-V group compound semiconductor or II-Vl group compound semiconductor on the substrate, it is possible to control the growth rate of a monoatomic layer over the entire surface of the growth substrate, and to create a high-quality compound with few lattice defects and impurities. This invention discloses a technique that enables the growth of semiconductor thin films and Peter structures with extreme steepness. This summary is provided solely for the purpose of quickly accessing the technical contents of the present invention, and does not have any influence on the technical scope of the present invention or the interpretation of rights. .

[Prior art J As a method of forming a compound semiconductor thin film on a substrate, metal organic pyrolytic growth (NOCVD) method single molecule beam epitaxy (
MBE) method, atomic layer epitaxy (ALE) method, and molecular layer epitaxy (MLE) method are known.

Examples of metal-organic pyrolysis vapor phase growth methods include H, M, Manas
The paper by Svit et al. (J, EIectrochem, So
c, 12G (1973).

568). In this method, as shown in FIG. 2, an organometallic compound and a hydride are transported onto a heated substrate together with a hydrogen carrier gas, and a compound semiconductor thin film is formed on the substrate by thermal decomposition. Taking GaAa, an m-v group compound semiconductor, as an example,
Trimethylgallium (cn
3) Arsine A5H, a hydride of 3ca and As
3 diffuses while being decomposed in the velocity boundary layer 2 formed near the substrate, and the completely decomposed Ga atoms and As atoms adhere to the substrate surface, and a GaAs crystal grows. Trimethyl gallium (TMG) hardly decomposes outside the boundary layer, and almost 100% decomposes on the substrate surface.

A concentration gradient of trimethylgallium will exist in the boundary layer. Since the growth rate is approximately proportional to this concentration gradient, the growth rate increases in the upstream region where the boundary layer is thin, and the growth thickness decreases downstream as shown in FIG. This non-uniformity of the growth thickness within the substrate plane has been the biggest drawback of the conventional metal-organic pyrolysis vapor phase growth method. In addition, in recent years, there has been an increase in the development of semiconductor devices with ultrafine structures such as quantum well structures and superlattice structures, and in this case, epitaxial technology that can control monoatomic layers has become required. In the organometallic pyrolysis vapor phase growth method, since the growth rate is rate-determining the rate of raw material supply, it is almost impossible to require controllability of a monoatomic layer over a wide area within the substrate surface.

Molecular beam epitaxy method is, for example, L, Chang at
at is J, Vac, Sci, Technol, Vol.
, 10. No. 5, pH (1973), the raw material elements, in the case of GaAs crystal, Ga and As, are heated in a high vacuum and deposited as GaAs on the substrate, which is also done within the plane of the substrate. It has been difficult to control the monolayer over a wide range of

Atomic layer epitaxy method (U.S. Pat. No. 4,058,430:1
977) as an improvement of molecular beam epitaxy.
This method, proposed by Tola et al., alternately supplies each semiconductor element in a pulsed manner to deposit monoatomic layers on the substrate alternately.The film thickness can be controlled with atomic layer precision, but the crystallinity is not good. T., 5untola et al. on the formation of compound thin films by this method.

Th1n 5olid Film 85 (1980)
, 304; Proc, 8thIntern, Vacuu
m Congress (1138G) Vol, 1
．． p401; Appl, Phys, Lett, 3B (1
981), 131 and many other papers, most of the compounds formed are ■-■ group compounds and oxides, and regarding m-v group semiconductors, IJSP 4,
An example of GaP is only introduced in 058,430,
There are no reports on GaAs, AnAs, etc.

The molecular layer epitaxy method was proposed by Nishizawa et al. as a method to improve the atomic layer epitaxy method (IEICE Technical Research Report Vol. 1.84. No. 127 pp. 73-78
), this method proceeds through monomolecular layer adsorption of raw material molecules, chemical reaction, and desorption of reaction products. 4. Showing a schematic diagram explaining the rEiK growth mechanism, arsine is introduced onto a heated substrate 1 in a high vacuum and a monomolecular layer of arsine is formed by evacuation (a), the adsorbed arsine is thermally decomposed A monoatomic layer of As is then formed (b).

Subsequently, trimethyl gallium is introduced, and the trimethyl gallium decomposes on the substrate to form a monomolecular layer of GaAs (c), (d). The system is evacuated again and excess trimethyl gallium is removed. By repeating this process, growth progresses one atomic layer at a time.

However, in this method, the growth atmosphere is vacuum and there is no As in the atmosphere, and As is removed from the growth layer.
This has the disadvantage that it becomes S vacancies, which leads to the incorporation of impurities and the formation of deep impurity levels involving As vacancies. Furthermore, this method has the disadvantage that since hydrogen is not present, the methyl radicals formed by the decomposition of trimethylgallium are not reduced by hydrogen, and the carbon of the methyl radicals is incorporated into the growth layer and becomes carbon acceptors. Actual report example (
Nishizawa et al., total loss paper), the growth layer has a carrier concentration of 1019
c■-3 units of p type are shown, supporting the growth and carbon contamination of the layer by methyl radicals. Furthermore, this method has 2
Once trimethyl gallium is adsorbed, the system is evacuated, so trimethyl gallium is desorbed and the surface coverage decreases. There was a drawback that it became less.

[Problem to be Solved by the Invention 1] As described above, the conventional techniques have problems such as in-plane non-uniformity in the thickness of the grown compound, poor controllability of the monoatomic layer, poor crystallinity, and difficulty in growing the compound. It has drawbacks such as a narrow range of compounds, a lack of As in the grown GaAs, and contamination with carbon acceptors.

The present invention solves these drawbacks and provides a high-quality compound semiconductor thin film that has a wide range of applications, has monoatomic layer growth rate controllability over the entire surface of the growth substrate, has few lattice defects and impurities, and has an extremely high steepness. The purpose of the present invention is to provide a method and apparatus for growing a heterostructure with the following characteristics.

Means for Solving Problem 1 In the present invention, group V or
A trace amount of a hydride containing a group element is constantly flowed together with a hydrogen carrier gas, and the hydride is diluted to a slightly high concentration with hydrogen, and an organometallic compound containing a group Ⅰ or group Ⅰ element diluted with hydrogen. By alternately flowing a monoatomic layer of a group V or group Ⅰ element and a monoatomic layer of a group Ⅰ or group ① element on the substrate.

[Function] The function of the present invention will be explained with reference to FIG. 1 using GaAs, which is a group ①-V compound semiconductor, as an example. heated GaAs
A trace amount of arsine diluted to a first concentration with a hydrogen carrier gas is constantly flowed over the substrate (Figure 1 (a))
, the amount of arsine is diluted to such an extent that even if trimethylgallium (TNG) reaches it, it will not react with it to form GaAs. When flowing together, arsine is adsorbed to Ga atoms on the substrate surface and thermally decomposed to form As atoms and G.
The aji atoms combine and an As monoatomic layer is formed on the substrate. (FIG. 1(b)), adsorption and decomposition proceed until the substrate surface is covered with a monoatomic layer of As. When an As monoatomic layer is formed, the adsorption between As atoms and arsine is weak, so the arsine that is subsequently transported leaves the system without being adsorbed, thus stopping the flow of high-concentration arsine. , purge excess arsine (Fig. 1 (C)), and flow trimethylgallium diluted with hydrogen (Fig. 1 (d)).
) Limethylgallium is strongly adsorbed to the As monoatomic layer on the substrate and is thermally decomposed to bond Ga atoms and As atoms to form a Ga monoatomic layer on the As monoatomic layer.

That is, a GaAs monolayer is formed on the substrate. G
Trimethylgallium, which arrived after the formation of the monoatomic layer a, leaves the system because its adsorption with Ga atoms is weak (,G
a After forming a monoatomic layer, stop the flow of trimethyl gallium and purge excess trimethyl gallium (Figure 1 (a)),
After that, by repeating the flow of arsine diluted to a relatively high concentration with hydrogen and the flow of trimethylgallium diluted with hydrogen, a monomolecular layer of GaAs is grown uniformly over the entire surface of the GaAs substrate every cycle. 0 In the method of the present invention, since dilute arsine is constantly flowing, As is removed from the formed GaAs.
does not escape, and since hydrogen gas is constantly flowing, the methyl groups generated by the decomposition of trimethyl gallium are reduced by hydrogen and become methane, so they do not dissolve into the compound, and therefore there is no contamination of carbon acceptors.
In addition, in this explanation, the repeating process of arsine → trimethyl gallium was explained, but even if the order of trimethyl gallium → arsine is repeated, the A on the surface of the GaAs substrate is first
The only difference is that trimethylgallium is strongly adsorbed to the s atom and decomposed to form a Ga monoatomic layer, but the subsequent process and action are exactly the same as repeating arsine→trimethylgallium.

[Example 1 Examples of the present invention will be described in detail below.

Example 1 A GaAs thin film was grown on a GaAs substrate. The substrate was a single crystal with a (100) growth plane.Arsine AsH3 was used as a hydride of a group V element, and trimethylgallium (Cl3)3Ga was used as an organometallic compound containing a group II element.

Fig. 5 shows an outline of an embodiment of the apparatus of the present invention.In Fig. 5, 1 is a substrate, 3 is a reaction tank, 4 is a substrate support, 5 is a heating device such as a high-frequency coil, 8 is piping, and vl to v8 are valves. be. Adjust valves V,,V,.

A hydrogen carrier gas and a trace amount of arsine AsH3 diluted with hydrogen are constantly allowed to flow through the reaction tank.

Operate valves V, , V, , Vo, and v to flow the required amount of arsine and trimethyl gallium (TMG).

Vs, V, is a heterostructure compound semiconductor explained in later examples, for example, Aloj; Ga, , Ag-G
aAs-A lo, 5 Ga(,, This is for flowing trimethylaluminum (TMA) when forming a gAss film, and is not necessary for forming a single-structure thin film such as GaAg. Valve Va, V4. V6゜V7(V, ,
In V,), the 6 reaction vessels in which the raw material gas can be introduced at time intervals determined by the control device 7 are shown as vertical ones, but it is of course possible to use horizontal reaction vessels.

First, arsine, which is kept flowing together with hydrogen gas, will be explained. This is to prevent As from being removed from the formed GaAs, and trimethylgallium (TNG)
In a static state, the substrate surface (solid phase) and the gas phase are in an equilibrium relationship, and the partial pressure of Ag species in the gas phase at a certain temperature is Uniquely determined. However, since the actual growth process is a dynamic state, it is necessary to constantly compensate for the equilibrium dissociation pressure of Ag species at that temperature. The thermal decomposition efficiency of arsine as a raw material to supplement As species is most dependent on temperature. Strictly speaking, the thermal decomposition efficiency depends on the residence time of arsine on the substrate, that is, on the hydrogen flow rate, but this dependence is small. Figure 6 shows the results of investigating the change in the amount of GaAs grown on the substrate depending on the arsine concentration when trimethylgallium with a molar fraction of 1 x 10-4-' was flowed 3600 times intermittently at 1-second intervals. The growth amount was measured by observing the cleaved cross section of the substrate with a scanning electron microscope at a magnification of 50,000 times.
As can be seen from the figure, at a temperature of 400 DEG C., no growth of GaAs could be observed in the AsH3 molar fraction range of 0 to 1.times.10@-4-'. As the temperature rises, the arsine concentration at which GaAg does not grow shifts to the lower concentration side, and 500
4X10-5 mole fraction at °C, 2X10-5 at 550 °C
When the mole fraction exceeds 5, GaAs grows. Same AsH
Even when compared at a mole fraction of 3, the amount of growth increases as the temperature rises. When the substrate temperature exceeds 550° C., trimethylgallium decomposes and Ga condenses on the substrate.

From the above results, it is derived that the concentration of arsine (first concentration) that is constantly flowed together with the hydrogen carrier gas is desirably 4X10-' mole fraction or less, particularly 2X10-5 mole fraction or less.

Next, arsine diluted to a second concentration for forming an As monoatomic layer on a substrate will be explained.

The substrate temperature is 450°C, the hydrogen flow rate is constant at 10 g/min, and arsine with a mole fraction of 1X1G-S is constantly flowing together with the hydrogen carrier gas.
10-4-' trimethyl gallium (TIIIC) in the 7th r! 4, they are introduced alternately at 1 second intervals.

After changing the concentration of arsine and repeating 3800 cycles each, the thickness of the GaAs film formed on the substrate was measured. The results are shown in FIG. 8. The amount of growth initially increases with the concentration of arsine, but becomes a constant value of 1.02 ILm when the concentration exceeds 1.times.10@-3 molar fraction. Converting this value to the value for one cycle gives 2-83A, which is G
It corresponds to the thickness of one monolayer of aAa. Therefore, it is desirable that the second concentration of arsine is 1×1 G−3 mole fraction or more.

In addition, the introduction time of arsine in each cycle was 2 seconds,
Even when the time was changed to 3 seconds, 4 seconds, and 5 seconds, no change was observed in the amount of growth.

Next, trimethyl gallium for forming the Ga monoatomic layer will be explained.

The substrate temperature, hydrogen flow rate, and arsine concentration that is constantly flowing are as follows:
Same as the case of arsine mentioned above, 450°C,
10 fL/min, 1 x 10-4-' mole fraction. 7th
Trimethyl gallium and arsine at a molar fraction of 1×10-4''-' were alternately introduced onto the substrate at the same time intervals as in the time chart in the figure, and the grown film thickness was measured after 3B00 cycles were repeated.Grown film thickness varies as shown in Figure 3 depending on the concentration of trimethylgallium introduced, and is 1 x 10-
A constant value of 1.021 Lm is maintained at a concentration of 4" mole fraction or higher, and this value corresponds to a GaA+ monomolecular layer of 2.83 A" in one cycle.The introduction time of trimethylgallium in each cycle I tried extending it to 5 seconds, but there was no change in the amount of growth.

The growth temperature (substrate temperature) was varied using the heating device shown in the apparatus shown in FIG. 5, and its influence on the growth amount was investigated. Hydrogen flow rate 1017 minutes, concentration of arsine constantly flowing 1X10-5
Mole fraction, concentration of arsine intermittently flowing 1 x 10-4-
'Mole fraction, concentration of trimethylgallium 1 x 10-4-
The molar fraction, introduction and stop times in each cycle were each 1 second as shown in FIG. The amount of growth after 3800 cycles is shown in Figure 10. No growth was observed at long temperatures of 400°C, and when the temperature exceeded 430°C, the growth thickness became close to 1 lumen, and from around 450°C to 500°C.
The growth amount per cycle is maintained at 1.02 ILm, which corresponds to the thickness of a monomolecular layer of GaAs, until the growth temperature slightly exceeds 520° C., and the growth amount increases rapidly when the growth temperature exceeds 520° C. When the growth temperature is 550° C., the amount of growth exceeds that of a single atomic layer, and the growth surface becomes rough. Therefore, the desirable growth temperature is 430-520℃, especially 4
The temperature is 50-500°C.

In previous experiments, the introduction of arsine to grow an As monoatomic layer and the introduction of trimethylgallium to grow a Ga monoatomic layer were performed for 1 second each, for example, as shown in Figure 7. There was a downtime during which hydrogen carrier gas and a very small amount of arsine were allowed to flow. This is to drive out excess arsine or excess trimethylgallium to completely replace the raw material gas. In the apparatus of the invention as outlined in FIG.

The source gas can be replaced in less than 1 second. Substrate temperature 45
0°C, hydrogen flow rate 10 i/min, concentration of arsine constantly flowing
Assuming that X10 = mole fraction, the concentration of arsine for forming an As monoatomic layer is lX10-3 mole fraction, and the concentration of trimethyl gallium is 1×10-4-' mole fraction, the time chart shown in FIG. t2 and t4 were changed * t,,
Both j3 are fixed to 1 second and 1. , 14 was varied from 1 second to 5 seconds, but no change was observed in the amount of growth.

In Figure 11, the (ioo) plane of GaAs is used as the growth surface, the growth temperature is 450°C, the hydrogen flow rate is 10 i/min, and the concentration of arsine that is constantly flowing is 1 x 10-4-5 molar fraction, 1 x 10-4.
- 1 second introduction of 3 mole fraction of arsine, 1 second stop, LX
1 s introduction of trimethylgallium at IO”−’ mole fraction,
The growth thickness of GaAs when 3600 cycles are repeated, with a 1 second stop being considered as 1 cycle, is shown along the length direction of the substrate.
This is the result of the measurement. The measurement was carried out by scanning electron microscopy observation of the cleavage plane.

The growth thickness was uniform, and the decrease in growth thickness from the upstream end of the substrate toward the downstream, which was observed with conventional metal-organic pyrolysis vapor phase growth, was not observed, and a uniform growth layer was obtained over the entire surface of the substrate. . Also, the amount of growth per cycle is 2.83X
This shows that monomolecular layer growth of GaAs has been achieved. Figure 12 is a diagram showing the dependence of the growth thickness on the number of cycles under the same conditions as the example shown in Figure 11. The growth thickness is proportional to the number of cycles, and this figure also shows that the amount of growth per cycle is is estimated to be 2.83 A, indicating single monolayer growth due to the formation of a monoatomic layer. In the examples so far, the cycle of AsH3 introduction → stop → TIIIG introduction → stop was described as shown in the time chart of FIG. 7, but the growth of the compound is exactly the same even if starting from the introduction of DMG.

The carrier concentration obtained from the electrical properties of the grown layer is p, and in the type 10"C layer-3, an improvement of nearly two orders of magnitude in purity was observed compared to a method that does not use hydrogen. This is due to the methyl This shows that the radical is reduced to methane by the hydrogen introduced according to the present invention as shown in formula (1), and is difficult to be incorporated into the crystal.

(CH3)3Ga+ -)1. +3GH4+Ga
(1) In addition, the photoluminescence intensity of the grown layer is comparable to that of a sample with the same carrier concentration produced by liquid layer epitaxial growth, indicating that it is a high-quality grown layer with few crystal defects. This is due to the prevention of As from leaving the growth layer. Note that even if the first dilution concentration of arsine is set to lX10 = molar fraction, it is effective to prevent As from being removed.

Furthermore, by using triethyl gallium instead of trimethyl gallium, the electrical characteristics of the grown layer become n-type 10 cm, further improving the purity. In the case of triethylgallium, ethylene is produced as a by-product through the reaction, and carbon is difficult to incorporate into the crystal due to its woody nature, so that a grown layer with higher purity can be obtained than when using a methyl-based metal compound.

Example 2 A semiconductor thin film of a ■-v group compound other than GaAs was formed.

Trimethylaluminum ((H3)3A
n and arsine AsH3, AlAs substrate (io
o) A thin film of AJLAs was grown on the surface. The method of introducing the raw material gas is that the TMG in the example shown in FIG. 7 is replaced with trimethylaluminum HA (concentration 1×10=mole fraction), and other than that, both the concentration and time are the same. The amount of growth after repeating 3600 cycles at a growth temperature of 450° C. was 1.02 g, and a monomolecular layer of AnAs was formed in each cycle.

To form GaP, PH3 can be used as a hydride and trimethylgallium can be used as an organometallic compound.
The first concentration of PH3 is 1 x 10-4-5 mole fraction, the second
c11 degrees tx to-3 more L, fraction, TMG (7
) 11 degrees IX 1G-' mole fraction, and the growth was performed on the GaP substrate (10G) surface for 3600 cycles at the same time intervals as in FIG. Growth amount at growth temperature 450℃ is 0.98I
This is the L layer, and a monomolecular layer of GaP is also formed in each cycle.

Trimethylindium (CH3)3In (concentration 1×
10-4-'molar fraction) and SbH3' (concentration lX10
-' and 1×10-4-' mole fraction), at a growth temperature of 450°C, and at the same time intervals as in FIG. Growth was performed on a 9b substrate (10G) surface for 3800 cycles. The growth amount was 1.17%, and an InSb monolayer was formed in each cycle.

In the same manner, (OH3) 3AJL and PH3 were used to make an AfLP thin film, (CH3) JAM and SbH3 were used to make an A-view Sb thin film, (OH3) 3Ga and sb■3 were used to make a Ga5bfif! K, (CH3)3 In and PH3
((H3,)31.n and As
An InAs thin film can be formed using H3.

Growth thickness after 3600 cycles is ARP 0.98 final layer,
1.1101L for AJISb, 1.11 for GaSb
01L, 1.081L layer for InP, and 1.09IL layer for InAs. In either case, the growth is uniform on the substrate, there are no vacancies of group V elements, and no carbon acceptors are introduced.

In these cases, as in the case of GaAs, triethylgallium, triethylaluminum, triethylaluminum,
If triethylindium is used, higher purity crystals can be obtained.

The effect of the growth temperature and the effect of the concentration of the source gas are the same as in Example 1.

Example 3 The present invention can also be applied to II-VI group compound semiconductors.

Dimethylzinc (OH, ) Zn as an organometallic compound.

Hydrogen sulfide H2S was used as the hydride, and a ZnS substrate (1
A 5g ZnJ film was formed on the 0G) surface. Growth temperature 45
0°C, hydrogen carrier gas flow rate 101/min, constant flow H
The concentration of 2S is 1 x 10-4-'' mole fraction, the concentration of H2S is 1 x 10-4-3 mole fraction to form an S monoatomic layer,
The concentration of (OH3)2Zn was set to 1 x 10-4-' molar fraction, and as shown in the time chart of Fig. 7, heat was introduced and stopped for 1 second repeatedly. The growth thickness after 3800 cycles was 0.9 full carbon dioxide, and the growth thickness per cycle corresponded to a monomolecular layer of ZnS.

Using dimethylzinc (0M3)2Zn and HzSe,
A Zn5e thin film was formed on the (100) surface of the Zn5e substrate. Growth temperature 450 °C, hydrogen flow rate 10 M/min, concentration of Ho5e constantly flowing 1 x 10 = mole fraction, concentration of H2Se to form a Se monoatomic layer 1 × 10-4-3 mole fraction, (CH3)2Zn The concentration was set to 1 x 10-4 raw mole fraction, and the raw material gas was introduced and stopped using heat for 1 second. 3
The amount of growth after 600 cycles was 1.021 La, and a monomolecular layer of Zn5e was formed every 1 cycle.

Using dimethylmercury (CO3)2Hg as an organic metal and H2Se as a hydride, a HgSe substrate (100) was used.
A Hg'J4 film can be formed on the surface in exactly the same way as in the case of Zn5e. Growth amount after 3800 cycles is 1.1
0 JLm, which means that a monomolecular layer of HgSe was formed in each cycle.

In either case, growth occurs uniformly over the entire surface of the substrate, and ■
The generation of vacancies of group atoms and the intrusion of carbon acceptors are small, and a highly pure thin film can be obtained.

If (C2J)2Zn and (02H5)2Hg are used instead of (an,)2zn, ((J3),)Ig(7), the intrusion of carbon acceptors will be further reduced.

The effects of the growth tube and the concentration of the raw material gas are the same as in Example 1.

Note that in Examples to Example 3, examples are described in which a single crystal is used for the substrate, but a polycrystalline substrate may also be used depending on the type and application of the compound semiconductor to be formed.

Example 4 Using the apparatus shown in FIG. 5, arsine A was used as the raw material gas.
AM6,5 using sH3,)limethylgallium (T)IG), )limethylaluminum (TMA)
Ga6. ! ;As-GaAs-116,g Gao,
5A+(7) heterostructure compound semiconductor thin film made of GaAs
It was formed on the (10G) plane of the substrate.

The formation conditions were a hydrogen flow rate of 1017 minutes, an arsine concentration of 1 x 10-5 molar fraction that was constantly flowing, and the concentrations of arsine, MG, and TMA to form a monoatomic layer were 1 x 10', respectively.
-3 mole fraction, IXIG-4 mole fraction, 1 x 10-4-
' is the mole fraction. As shown in the time chart shown in FIG. 13(a), this raw material gas is subjected to 100 cycles of arsine introduction, stop, TMG introduction, stop, MA introduction, and stop at intervals of 1 second each, and then, as shown in the time chart shown in FIG. The cycle of arsine introduction, stop, TNG introduction, and stop shown in b) was repeated 10 times.
The cycle was repeated, and the same cycle as the first was repeated 100 times.

By the above operations, a heterostructure as shown in FIG. 14 is produced, and the thin GaAg layer becomes a quantum well.

In a quantum well structure similar to this one fabricated by the conventional IRE method or N0CVD method, the GaAs quantum well emission has a wavelength of 71.
0 nm, and the half-value width is 15 to 30 meV, which is wider than the theoretical value and reflects the unevenness of the hetero interface.

On the other hand, according to the present invention, the wavelength is 710n layer, the half width is 8meV
The half-width expected from the unevenness of one atomic layer at the heterointerface 3
It showed an extremely narrower half-width than the 0 layer eV. From this, it can be determined that there is no unevenness at the hetero interface.

Furthermore, even in a two-dimensional electron gas structure in which electrons travel across a hetero-interface, in the conventional method, electrons are scattered due to the unevenness of the interface, and the mobility is suppressed to be lower than a theoretical value. However, in the heterointerface produced according to the present invention, there is no scattering due to the unevenness of the interface, and the two-dimensional electron gas mobility can be significantly improved.

Furthermore, by taking advantage of the controllability of a monoatomic layer, for example, as shown in FIG.
Ga 6.ヮIt becomes possible to produce mixed crystals such as 5As.

The electrical-optical properties of the mixed crystal prepared in this way are much superior to those of conventional mixed crystals in which homologous atoms are arranged in a statistically random manner.For example, in conventional mixed crystals,
Conduction electrons were scattered by the potential field created by randomly arranged atoms, and their mobility was suppressed to a low level. However, in mixed crystals in which atoms are arranged regularly, the potential field becomes periodic and the mobility significantly increases. Improvement becomes possible.

〔Effect of the invention〕

As explained above, in the present invention, while flowing a hydride containing a trace amount of a group V or group II element together with a hydrogen carrier gas onto a substrate, an organic metal containing a group III element or a group III element diluted with hydrogen is used. A compound and a hydride containing a group V or group II element diluted with hydrogen are alternately introduced onto the substrate to form a monoatomic layer of a group m or group II element and a V group element on the substrate.
Monoatomic layers of group elements or group (ii) elements are formed alternately, and a (i)-v group compound or (ii)-(ii) group compound semiconductor is formed as a stack of molecular layers. In this way, the adsorption and thermal decomposition of the molecular layer is always carried out under a constant pressure, so the surface coverage does not change, the compound grows uniformly over the entire surface of the substrate, and the growth thickness changes in one cycle of introducing the raw material gas. is the thickness of the monolayer of the compound formed. In addition, since a hydride containing a small amount of Group V or Group II elements such as arsine is constantly flowing, the generation of vacancies of Group V or Group II elements such as As is extremely small.Also, since hydrogen gas is constantly flowing, Due to the reducing action of hydrogen, free methyl groups become methane, so they are not mixed into the growth layer, carbon acceptors are reduced, and a highly pure growth layer is obtained. This point can be further improved by using an organometallic compound having an ethyl group.

The compound semiconductor having a heterostructure formed by the method of the present invention has the advantage that there is no unevenness at the hetero interface, and that the quantum well light emission has a narrow half-width because it is light emission from a single quantum level. Furthermore, when electrons travel across the heterointerface, there is no scattering due to the unevenness of the interface.

Furthermore, according to the present invention, ordered mixed crystals can be easily produced.

According to the present invention, a high-purity compound semiconductor can be uniformly formed over a wide area of a substrate.

It is possible to form compound semiconductors with heterostructures and ordered mixed crystals with an atomically average interface.

It can be widely applied to FETs, laser elements, etc.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the present invention in detail, Fig. 2 is a diagram showing conventional metal organic pyrolysis vapor deposition (MOCVD).
Figure 3 is a diagram showing the growth thickness distribution of compound semiconductors by the xocvn method. Figure 4 is a diagram explaining the operation of the conventional molecular layer epitaxy (MLE) method. Figure 6 is a diagram showing the effect of the concentration of constantly flowing arsine; Figure 7 is a time chart as an example of raw material gas introduction; Figure 8 is a monoatomic As Figure 9 shows the effect of the concentration of arsine forming the layer; Figure 9 shows the effect of the concentration of trimethyl gallium; Figure 1O shows the effect of growth temperature on the amount of growth; Figure 11 shows the method of the present invention. Figure 12 is a diagram showing the dependence of the GaAs growth thickness on the source gas introduction cycle, and Figure 13 is the distribution of the source gas for forming a heterostructure compound semiconductor. A time chart diagram as an example of introduction. FIG. 14 is a diagram illustrating the formed heterostructure, and FIG. 15 is a diagram illustrating the formed ordered mixed crystal. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Velocity interface layer, 3... Reaction tank, 4... Substrate support stand, 5... Heating device, 6... Piping. 7...Control device. Agent Yoshi Tani, patent attorney - Figure 1,
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Claims (1)

[Scope of Claims] 1) An organometallic compound containing a group III or II element and a hydride containing a group V or VI element are transported onto a heated substrate and pyrolyzed to form a group III-V or II- In a compound semiconductor thin film formation method in which Group VI compound semiconductors are grown on a substrate, I
A first compound that does not form a group II-V compound or a group II-VI compound.
introducing the hydride diluted with hydrogen to a second concentration higher than the first concentration onto the substrate while constantly flowing a hydride containing a Group V or VI element diluted to a concentration of , a step of stopping the introduction of the hydride diluted to the second concentration; a step of introducing an organometallic compound containing a group III or group II element diluted with hydrogen onto the substrate; and a step of introducing the organometallic compound containing a group III or group II element diluted with hydrogen. A compound semiconductor thin film forming method characterized by repeating the process of stopping the introduction of. 2) The compound semiconductor thin film forming method according to claim 1, wherein the temperature of the substrate is 430°C or more and 520°C or less. 3) The method for forming a compound semiconductor thin film according to claim 1, wherein the first concentration of the hydride is 4×10^-^5 mole fraction or less. 4) The method for forming a compound semiconductor thin film according to claim 1, wherein the second concentration of the hydride is 1×10^-^3 mole fraction or more. 5) The dilution concentration of the organometallic compound is 1×10^-^4
2. The method for forming a compound semiconductor thin film according to claim 1, wherein the molar fraction is greater than or equal to the mole fraction. 6) The method for forming a compound semiconductor thin film according to any one of claims 1 to 5, characterized in that two types of organometallic compounds containing different metal elements are introduced onto the substrate as the organometallic compound. 7) The method for forming a compound semiconductor thin film according to any one of claims 1 to 6, wherein the organometallic compound is an organometallic compound having an ethyl group. 8) Transport an organometallic compound containing a group III or group II element and a hydride containing a group V or VI element onto a heated substrate, and convert the group III-V or group II-VI compound semiconductor to the substrate by thermal decomposition. In the device for forming a compound semiconductor thin film that is grown on a compound semiconductor thin film, there is one or more systems that transport the organometallic compound, and the transport time and transport amount of the one or more organometallic compound transport systems and the system that transports the hydride. What is claimed is: 1. A compound semiconductor thin film forming apparatus comprising: a control system for controlling the hydride, and a system for transporting a hydride diluted by a hydrogen carrier gas.