JPH078757B2 - Compound semiconductor thin film formation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a compound semiconductor thin film, and more particularly to a method for forming a III-V group compound semiconductor thin film having a controlled high impurity concentration.

[Conventional technology]

As a process technology for GaAs integrated circuits such as GaAs MESFET, a technology for forming a low resistance ohmic electrode is required.
Therefore, a method of introducing a high concentration n ⁺ layer is adopted.
The high-concentration n ⁺ layer is formed by ion implantation or epitaxial growth. The ion implantation method is suitable for fine processing, but has many problems such as defect introduction by implantation and an annealing process.

Metal-organic vapor phase pyrolysis growth (Metal-Organic Growth), which is a type of epitaxial method, is a method for forming a high-concentration impurity-doped III-V group compound semiconductor thin film with excellent film thickness controllability and mass productivity. Chemical Vapor Deposition;
MOCVD) method. Si doping of GaAs which is a typical III-V group compound semiconductor will be described as an example. Organic gallium compounds such as trimethylgallium, arsine (AsH ₃ ) which is a group V hydride, and silane (SiH ₄ ) which is a group IV hydride are placed on a substrate heated to a high temperature (650 to 750 ° C.).
It was supplied together with a hydrogen carrier gas to form an n-type GaAs layer doped with Si produced by thermal decomposition. However, there are no reports of doping above 5 × 10 ¹⁸ cm ^-3 (Duchemine e
t al: J. Electrochem. Soc. 126, 1134 (1979)). Similarly I
Germanium (GeH ₄ ) which is a group V hydride (Duchemin et al
N) of 5 × 10 ¹⁸ cm ⁻³ or more even when hydrogen selenide (H ₂ Se) and hydrogen sulfide (H ₂ S) which are group VI hydrides are used.
Type doping was not possible (Bass and Oliver: Inte
rnational Symposium on GaAs and Related Compounds,
St.Louis, 1976, edited by LFEastman (Inst.Phys.Con
f.Ser.No.33b, London, 1977), P.1). On the other hand, when p-type doping was attempted using group II organometallic compounds dimethylzinc and diethylzinc, it was impossible to dope more than 10 ¹⁹ cm ^-3 (Aebi et al: J. Cryst.Growth).
55 (1981) 517).

As a method for forming a group III-V compound semiconductor thin film in which only one atomic layer of impurities is doped, an atomic layer doping method utilizing a molecular beam epitaxial (MBE) method and a metalorganic pyrolysis vapor phase epitaxy (MOCVD) method can be mentioned. . Here, a case where GaAs, which is a typical III-V group compound semiconductor, is doped with Si by one atomic layer will be described as an example.

In the MBE method, first, GaAs obtained by heating Ga and As in a high vacuum is used.
Evaporate on the substrate. Then, the Ga flux is stopped, the GaAs crystal growth is stopped, and As and Si atoms are vapor-deposited on the As atomic plane. Then, by depositing Ga and As again,
It is possible to obtain a structure in which As crystal is doped with one atomic layer of Si. The maximum surface density in this method is currently 5 × 10 ¹² cm
^-2 (S.Sasa, S.Muto, K.Kondo, H.Ishikawa and SH
iyamizu: Jpn.J.Appl.Phys.24 (1985) L602). In order to obtain this surface density, it takes 300 seconds or more to deposit As and Si atoms, and the efficiency of Si atom incorporation is extremely poor.

In the MOCVD method, first, an organic gallium compound and arsine are supplied onto a heated GaAs substrate together with a hydrogen carrier gas. Then, the supply of the organic gallium compound is stopped, arsine and silane are supplied, and then the arsine and the organic gallium compound are supplied again, whereby Si is added to the GaAs crystal.
An atomic layer doped structure is formed. The maximum areal density of this method is 10 ¹² cm ^-2 (H. Ohno, E. Ikeda and H. Hasegaw
a: Jpn.J.Appl.Phys.23 (1984) L369) and very low.

In the MBE method, a structure in which Ge is doped by only one atomic layer has been produced, but a high areal density has not been obtained (CEC
Wood, G.Metze, J.Berry and LF Eastwan: J.Appl.Phys.5
1 (1980) 383).

When Si is doped into GaAs by the conventional method, the AsH excess state, that is, the As stabilizing surface is always used for doping. If Si doping is performed on the Ga surface by the conventional method,
Since the high vapor pressure As atoms on the lower surface of the Ga plane fly and the thin film surface becomes very rough, Si doping on the Ga plane could not be performed.

In addition, the report of TF Kuech et al. (Appl.Phys.Lett 44 (1984)
986), the doping efficiency of SiH ₄ strongly depends on the growth temperature, and the higher the temperature, the higher the carrier concentration obtained. The experimental results indicate that the temperature distribution in the growth substrate plane impairs the in-plane uniformity of doping, and in fact, Kuech et al. Reported a non-uniform doping concentration. Furthermore, when trying to dope at a high concentration,
It was necessary to raise the growth temperature. This means that the diffusion of doping atoms causes a blur in the profile.

As described above, the doping on the As-stabilized surface had a weak adsorbing power of the doping molecule and desorption, so that the doping concentration was limited.

[Problems to be solved by the invention]

The present invention overcomes the above-mentioned conventional drawbacks and enables high concentration doping of a compound semiconductor at a relatively low temperature, a small diffusion of a dopant between a doped layer and an undoped layer, and a crystal surface and An object of the present invention is to provide a method for forming a compound semiconductor thin film having few defects at a doping interface or a hetero interface in a crystal.

[Means for solving problems]

In order to achieve such an object, the compound semiconductor thin film forming method of the present invention is diluted with a hydrogen carrier gas on a substrate to a first concentration which does not react with an organometallic compound to form a III-V group compound. A process of introducing arsine diluted to a second concentration higher than the first concentration by a hydrogen carrier gas onto a substrate while constantly flowing arsine (AsH ₃ );
The step of stopping the introduction of the arsine diluted to the second concentration and the step of introducing the organometallic compound containing the group III element diluted with the hydrogen carrier gas onto the substrate are repeated to form the compound semiconductor thin film on the substrate. In the forming method, silane (SiH ₄ ) is introduced together with an organometallic compound containing a group III element to dope the compound semiconductor.

Further, the compound semiconductor thin film forming method of the present invention reacts with an organometallic compound together with a hydrogen carrier gas on a substrate to form a III-
While constantly flowing a hydride containing a group V element diluted to a first concentration that does not form a group V compound, the hydride diluted to a second concentration higher than the first concentration by the hydrogen carrier gas is placed on the substrate. A step of introducing, a step of stopping the introduction of a hydride diluted to a second concentration, a step of introducing an organometallic compound containing a Group III element diluted with a hydrogen carrier gas onto a substrate, and an organometallic compound The introduction of
In the method of forming a compound semiconductor thin film on a substrate by repeating the process of introducing hydrogen halide diluted with a hydrogen carrier gas and stopping it, a compound containing a group IV element, a group VI element, or a group II element is formed together with the hydrogen carrier gas. It is characterized in that it is introduced onto a substrate to dope a compound semiconductor.

[Action]

According to the present invention, it is possible to dope a III-V compound semiconductor at a high concentration. Further, since the doping is performed by low temperature crystal growth, the diffusion of the dopant at the interface between the doped layer and the undoped layer is small. Further, a crystal having few defects can be obtained by using a method of introducing a hydrogen halide after forming an atomic plane of a group III element during crystal growth to remove surface defects and deep levels.

〔Example〕

Hereinafter, the present invention will be described in detail by way of examples with reference to the drawings.

FIG. 1 shows an outline of an apparatus used in the present invention. In the figure, 1 is a substrate, 2 is a reaction tank, 3 is a substrate support, 4 is a heating device such as a high frequency coil, 5 is piping, and V ₁ to V ₁₂ are valves. The valves V ₁ and V ₂ are adjusted so that a carrier gas and a small amount of a hydride of a Group V element diluted with the carrier gas are always flown into the reaction tank 2. V ₃ to V ₁₂ are valves for introducing a raw material gas for forming a compound semiconductor, an impurity gas for doping, and hydrogen halide, which will be described later, into the reaction tank 2. The gases shown in the figure are examples of them. The valves V ₃ to V ₁₂ are adapted to allow the introduction of a defined quantity of gas by the control device 6 at a defined time interval. Reference numeral 7 is a pipe for exhaust. The reaction tank 2 is shown as a vertical type, but it goes without saying that a horizontal type reaction tank can be used.

Example 1 A highly Si-doped GaAlAs ordered mixed crystal thin film was prepared. Using the (100) plane of GaAs single crystal as a substrate, triethylgaliu (TEG), triethylaluminum (TEA) and arsine (AsH ₃ ) as source gases, silane (SiH ₄ ) as an impurity source gas, and carrier gas Hydrogen (H ₂ ) was used.
The source gas and the impurity gas are introduced onto the substrate according to the timing chart of FIG. That is, the H ₂ flow rate is 10 l /
Minutes, while constantly flowing 1 × 10 ^-5 mole fraction arsine, 1 × 10 ^-3 mole fraction arsine and 1 × 10 ^-4 mole fraction TEG
Was introduced for 3 cycles at 1 second intervals to form three GaAs layers, and then 1 × 10 ⁻³ mole fraction of arsine and 1 × 10 ⁻⁴ mole fraction of TEA were introduced at 1 second intervals. 1 molecular layer of AlA
s layer is formed. Thus three layers of GaAs and one layer of A1As
An ordered mixed crystal of Ga _0.75 Al _0.25 As is formed when the layers are stacked alternately. It was confirmed from the reaction of the number of layers and the film thickness that the formed thin film was performing monomolecular layer growth, and from the result of X-ray diffraction that it was a controlled mixed crystal. To dope Si, when forming the intermediate layer of the three GaAs layers, SiH ₄ was added to the TEG.
Were mixed. The flow rate of SiH ₄ was kept constant at 2.5 × 10 ⁻⁷ mole fraction, and the Si concentration in the thin film formed was measured by a secondary ion mass spectrometer while changing the growth temperature. The results are shown in FIG. In the figure, the concentration of carbon, which is an impurity mixed from TEG or TEA, is also shown. As shown in the figure, according to this method, a high Si doping concentration of about 10 ¹⁸ cm ⁻³ is achieved at a substrate temperature of 500 ° C. or higher. On the other hand, carbon is not detected in the formed thin film in this growth temperature range.

FIG. 4 shows the carrier concentration at room temperature, and FIG. 5 shows changes in the sheet carrier concentration and electron mobility depending on the growth temperature. As shown in FIGS. 3 to 5, according to the method of the present invention, by treatment at a relatively low temperature of 500 to 650 ° C., the ordered mixed crystal semiconductor GaAlAs can be used at a high concentration for practical use.
It can be doped with Si.

The reason why such a high carrier concentration is obtained will be described with reference to FIGS. 6 (A) to 6 (C). When triethylgallium and silane are allowed to flow at the same time with a trace amount of arsine that does not contribute to growth, triethylgallium that reaches the growth surface is adsorbed on the As surface and decomposed into Ga atoms, forming innumerable Ga monatomic steps. (Fig. (A)). Simultaneously with the flow of silane, the silane molecule is adsorbed and decomposed on the Ga atom surface (Fig. 6 (B)), and the Si atom moves to the place where there is a step and is incorporated into the Ga site to serve as a donor (Fig. 6 ( C)). That is, SiH ₄ has a property of being more strongly adsorbed to the Ga surface than to the As surface, and moreover, by flowing simultaneously with triethylgallium, Si is incorporated into the Ga site before the number of Ga monatomic steps decreases. Therefore, it is considered that high-concentration doping was realized.

Example 2 A Si-doped GaAs thin film was formed on the (100) plane of a GaAs single crystal substrate. Arsine (As
H _3), was used trimethyl gallium as the organometallic compound containing a Group III element _{((CH 3) 3 Ga)} , silane as a hydride containing a group IV element (SiH _4). As shown in the time chart of FIG. 7, the hydrogen flow rate is kept constant at 10 l / min, and arsine in a 1 × 10 ⁻⁵ mole fraction is constantly flown together with the hydrogen carrier gas. Arsine, which is constantly flown with the hydrogen gas, is used to prevent the release of As from the formed GaAs, and has a concentration that does not form GaAs by reacting with TMG. Then, after introducing trimethylgallium (TMG) and silane each having a mole fraction of 1 × 10 ^-4 for 1 second, hydrogen chloride (HCl) having a mole fraction of 1 × 10 ^-4 was introduced for 1 second, and thereafter 1 × 10 ^{4 -Introduce a 3} mole fraction of arsine for 1 second. 36 as one cycle
Repeated 00 cycles. In this case, the grown film thickness was 1 μm.

Figure 8 shows the substrate temperature at 550 ℃ and the silane mole fraction at 10
The carrier concentration of the growth layer obtained when changing from ^-8 to 10 ^-3 is shown.

The obtained growth layers are all n-type and have a molar fraction of 10 ^-8 to 10 ^-4.
Has a comparative relationship with carrier concentration up to a molar fraction of 2 × 10 ^-4
At that time, the highest carrier concentration was 3 × 10 ²⁰ cm ⁻³ . FIG. 9 shows the carrier concentration when the silane mole fraction is set to 1 × 10 ⁻⁴ and the substrate temperature is changed from 450 ° C. to 650 ° C. A carrier concentration of 2 × 10 ²⁰ cm ^−3, which is independent of the growth concentration, was obtained from 500 ° C. to 650 ° C. The reason why such a high carrier concentration is obtained is as described in the first embodiment.

The effect of introducing HCl will be described. When TMG and silane are introduced to form a Si-doped Ga layer, some of Ga atoms form a two-layer structure as shown in FIG. If Arsine is flown on top of this without flowing hydrogen chloride, the Ga of the second layer
Is in the As position, so it is an anti-site detec
t), forming a deep level. An abnormal defect is generated from this defect and is observed as a surface defect. If hydrogen chloride is introduced after the introduction of trimethylgallium, Ga-Ga 2
Since Ga of the second layer of the layered structure is bonded to chlorine and the two-layered structure is broken, the number of surface defects and the deep level are reduced to 1/10 or less. As a result of investigating the relationship between the mole fraction of hydrogen chloride and the surface defect density, it was found that the effective hydrogen chloride concentration was 1 × 10 ⁻⁴ mole fraction or more. FIG. 11 shows the surface defect densities when HCl was flowed after introducing TMG (curve A) and when HCl was not flown (curve B). The concentration of arsine, which is constantly flown, is preferably 4 × 10 ^-5 mole fraction or less in order not to react with TMG,
The concentrations of TMG and arsine for crystal growth are preferably 1 × 10 ⁻⁴ mole fraction or more and 1 × 10 ⁻³ mole fraction or more, respectively, in order to perform monolayer growth.

Next, the doping amount was examined when the introduction timing of silane was changed. That is, the introduction of silane was changed into three ways: (A) 1 second immediately after the introduction of TMG, (B) 1 second immediately after the introduction of arsine, and (C) a constant flow with a small amount of arsine.
The concentrations of TMG, arsine, and hydrogen chloride and the introduction cycle were as described above, and the substrate temperature was constant at 550 ° C. The carrier concentration obtained in each case by changing the silane mole fraction is shown in FIG. Curve A is a carrier concentration when silane is flown after TMG, curve B is a carrier concentration when silane is flown after arsine, and curve C is a carrier concentration when silane is normally flowed. Curve D shows the carrier concentration shown in FIG. 8 when TMG and silane were simultaneously flown for comparison. In all cases, the carrier concentration is linearly related to the silane mole fraction over a wide range. This shows that the controllability of the carrier concentration is good. Comparing each curve A to D, the highest carrier concentration was obtained when TMG and silane were simultaneously passed (curve D), and the carrier density was high when silane was introduced immediately after TMG introduction (curve A). The carrier concentration decreases in the order of continuous silane flow (curve C) and silane flow immediately after the introduction of arsine (curve B). In the case of the curve A, since the silane is flown after the Ga layer is formed, there are fewer steps on the Ga surface than in the case of the curve D, and Si is less likely to enter, and the carrier concentration is lower than that of the curve D at the same silane mole fraction. . In the case of the curve C, Si in the As layer acts as an acceptor, which cancels out with Si as a donor in the Gs layer to lower the overall carrier concentration. Originally, it is difficult for Si to enter the As site, but it is considered that a monoatomic plane step of As occurs during the formation of the As plane, which increases the probability that Si enters the As site and increases the acceptor amount. However, even in this case, since a large amount of Si enters the Ga surface, the carrier concentration is 5 × 10, which is one digit higher than the conventional one.
¹⁹ cm ^-3 is obtained. The maximum carrier concentration of the curve B in which silane was introduced immediately after the introduction of arsine and the As surface was doped with Si is about 5 × 10 ¹⁸ cm ⁻³ .

Example 3 A GaAs crystal containing only one atomic layer of Si-doped layer was grown.

Arsine AsH ₃ as hydride of group V element, trimethylgallium (TMG) as organometallic compound containing group III element
Silane SiH ₄ was used as a hydride containing (CH ₃ ) ₃ Ga and a group IV element. A flow chart of the source gas is shown in FIG. The flow rate of hydrogen, which is a carrier gas, is kept constant at 10 l / min, and a small amount of arsine of 1 × 10 ⁻⁵ mole fraction is constantly flowed. This small amount of arsine is for preventing As from evaporating from the GaAs crystal when forming the Ga layer, and has a concentration that does not react with trimethylgallium to form GaAs.

First, turn 900 the arsine mole fraction 1 × 10 ^-4 of TMG, 1 × 10 ^-4 mole fraction of HCl and 1 × 10 ^-3 mole fraction by 1 sec
Cyclical flow is performed to form a non-doped GaAs layer. Then, the supply of TMG is stopped for 1 second to form an As-stabilized surface, on which TMG and silane are flown for 1 second to form one atomic layer of a Si-doped layer. Then, HCl, arsine and TMG are sequentially supplied again to form a non-doped GaAs layer. Figure 14 shows the growth temperature of 55.
The change in the sheet carrier concentration obtained when the silane concentration was changed to 0 ° C. is shown. The sheet carrier concentration is
Obtained by room temperature Hall measurement. The obtained sheet dope layers are all n-type and have a silane mole fraction of 2 × 10 5.
^At the time of ^-4 , the maximum value of the sheet carrier concentration was 1 × 10 ¹³ cm ^-2 . The non-doped GaAs layer has high purity, and a high concentration can be obtained by atomically doping Si. Figure 15 shows that the silane mole fraction is fixed at 1 × 10 ^-4 and the growth temperature is 450 ° C.
It is the figure which showed the carrier density when changing from 650 degrees Celsius to 650 degrees Celsius. From 500 ° C. to 650 ° C., a sheet carrier concentration of 5 × 10 ¹² cm ⁻² independent of the growth temperature was obtained. this is,
It is shown that the same sheet carrier concentration was obtained with the amount of silane smaller by one digit or more as compared with the conventional method.

The carrier concentration when Si was doped on one atomic plane was measured by the Schottky method. Using TMG and arsine as the source gas, a small amount of arsine diluted with hydrogen is constantly flowed on the GaAs (100) surface, while TMG, HCl and high concentration arsine are alternately flowed for 1 second each to form a GaAs thin film. Form. After the arsine introduction process after forming a thin film by repeating a certain cycle, silane is introduced for 1 second to dope Si on the As surface, then the normal process is repeated to form a thin film, and TMG introduction after repeating a certain cycle After the process of introducing HCl, silane is introduced and the Ga surface is doped with Si, and thereafter thin film formation is continued. Arsine concentration of 1 × 10 ^-5 mole fraction and 1 × 10 ^-3 mole fraction, TMG and HCl concentration of 1 × 10 ^-4 mole fraction, respectively, introduction time of 1 second, substrate temperature of 550
℃, the concentration of silane is 1 × 10 ^-4 mole fraction, the carrier concentration of the thin film crystal obtained by repeating 6000 cycles was measured by the Schottky method along the depth direction of the thin film.
Shown in Figure 16. Si concentrates on the particular side where it was introduced. The broadening of each peak is due to thermal vibration, and the magnitude of the half-width confirms that the thin film is due to monoatomic layer growth. As shown in the figure, Si is trapped in the Ga plane more than the As plane. Figure 17 shows S on a specific 1Ga plane.
As a method of doping i, a method of flowing silane together with TMG and a method of introducing silane after introducing TMG and introducing HCl are shown in comparison, and a low peak is obtained by introducing silane after introducing TMG. The Si-doped surface and the high peak correspond to the Si-doped surface where TMG and silane were simultaneously introduced.
In this way, the doping amount of Si in the monoatomic plane is higher in the Ga plane than in the As plane, and for the Ga plane, G
Higher carrier concentration can be obtained by forming the a-face than by introducing silane after forming the Ga-face. This result is the basis of the carrier concentration curve shown in FIG.

Thus, when forming a thin film, HCl is introduced to partially remove Ga in the Ga layer and the Ga layer is doped with Si to obtain a high-concentration doped layer with a low surface defect density. To be When applied to a GaAs integrated circuit, it is fatal that the surface defect density is high. Therefore, the yield can be improved by applying the method of the present invention.

Although silane is exemplified as the doping gas, as shown in Table 1, various gases can be used to obtain a high carrier concentration.

The present invention is directed to another III-V compound semiconductor, AlAs, In.
As, AlP, GaP, InP, AlSb, GaSb, InSb, AlGaAs, InGaAs, AlInA
s, AlGaP, InGaP, AlGaSb, InGaSb, InGaAsP, InGaAsSb, AlGaA
It can also be applied to sP and AlGaAsSb.

Example 4 A compound semiconductor having the structure shown in FIG. 18 was prepared. A 250 Å-thick Si-doped GaAs layer 12 was formed on a Si-doped n-GaAs substrate 11 (carrier concentration 5 × 10 ¹⁵ cm ^-3 ) by the following method. Growth temperature was 450 ℃ and diluted with hydrogen 1
1 × 10 ^-4 while constantly flowing × 10 ^-5 mole fraction of arsine
1 mole of TMG and 1 × 10 ^-4 mole fraction of silane are simultaneously added.
Second flow followed by 1 × 10 ⁻⁴ mole fraction of HCl for 1 second. Then, 1 × 10 ⁻³ mole fraction of arsine is flown for 1 second. By repeating this alternately, an n-GaAs film 12 having a carrier concentration of 2 × 10 ²⁰ cm ^-3 was grown. Au13 is vapor-deposited on it as shown in FIG. 18, while the AuGeNi alloy electrode layer 14 is formed on the lower surface of the substrate.
Was deposited and the current-voltage characteristics were measured. As a result, this contact resistivity is 5 × 10 ⁻⁸ Ω · cm ² or less, which is the lowest value ever reported.

Example 5 The present invention was applied to the fabrication of GaAs FET. As shown in FIG. 19, an n ⁺ GaAs layer 22 having a thickness of 0.1 μm was formed on the semi-insulating GaAs substrate 21 by the same method as described in Example 4. After that, by the usual lithographic technique, the source electrode 23, the gate electrode 24,
A drain electrode 25 was provided and a GaAs FET having the structure shown in FIG. 19 was produced. While the conventional method uses ion implantation for the n ⁺ layer, this method uses the crystal growth method and
Since HCl has been introduced to remove the Ga bilayer structure, there are few crystal defects in the n ⁺ layer. Further, since a high-concentration n ⁺ layer can be formed, depletion due to the influence of the surface is small and the source series resistance is low. When integrated, there is little variation in the characteristics of individual FETs, and the standard deviation of the FET pinch-off voltage is 1
It was as small as 00 mV or less, and the yield in the wafer was significantly improved.

Example 6 A compound semiconductor having a hetero structure was produced using the method of the present invention.

As shown in FIG. 20 (A), a 1 × 10 ⁻⁵ mole fraction of arsine, which was always diluted with hydrogen, was flowed on the (100) plane of a semi-insulating GaAs substrate, and 1 × 10 ⁻⁴ mole fraction was ^added . TMG, 1 × 10 ⁻⁴ mole fraction of HCl, and 1 × 10 ⁻³ mole fraction of arsine are alternately flowed for 1 second to form a 5000 Å thick GaAs layer. The carrier concentration of this GaAs layer is 5 × 10 ¹⁴ cm ^-3 . Then, as shown in Fig. 20 (B), (trimethylaluminum (TMA) + silane) → HCl → arsine → (TMG + silane).
→ HCl → arsine → (TMG + silane) → HCl → arsine →
(TMA + silane) → Introduce source gas in this order to form GaAs2 layer
Si-doped Al _0.33 Ga _0.67 As with alternating AlAs 1 layers
Grow an ordered mixed crystal layer of 500Å. Silane concentration is 1 × 10
^-5 mol fraction, carrier concentration of this ordered mixed crystal layer is 1 ×
10 ¹⁹ cm ^-3 . Then, as shown in FIG. 20 (C), a source gas is flowed in the order of (TMG + silane) → HCl → arsine to form a 50Å-layer Si-doped GaAs layer. The carrier concentration of this GaAs layer is 1 with the concentration of silane being 1 × 10 ^-4 mole fraction.
× 10 ²⁰ cm ^-3 . The growth temperature is 550 ° C. Thus, on the semi-insulating GaAs substrate 31 as shown in FIG. 21, an undoped GaAs layer 32, Si-doped Al _0.33 Ga _0.67 As layer 33, Si are sequentially formed.
A compound semiconductor with a Tehro structure having a doped GaAs layer 34 is formed. The Si-doped Al _0.33 Ga _0.67 As layer 33 is a two-dimensional electron supply layer, and the interface 35 with the undoped GaAs layer 32 is a traveling surface of the two-dimensional electron gas. The Si-doped GaAs layer 34 is an electrode layer.

In the FET manufactured from the hetero-structured compound semiconductor grown in this manner, HCl is introduced after the Ga layer is formed to remove the Ga double layer structure, so that the number of defects on the surface and each interface is small. Therefore, the yield of the IC is improved and the hetero interface has few defects, so that the two-dimensional electron gas travels at high speed. Furthermore, since this method allows crystal growth to be performed at a lower temperature than the conventional method, the diffusion of Si at the hetero interface is small, the hetero interface and the doping interface are aligned, and the electron mobility of the GaAs layer is not reduced, resulting in high speed. FET can be realized. Furthermore Si
Can be doped at a high concentration, so that the electrode can be grown by crystal growth.

When forming a Si-doped Al _0.33 Ga _0.67 As layer, FIG. 20 (B)
As shown in Fig. 22, instead of the method shown in Fig. 22, TMG and its 1
/ 2 amount of TMA may be flowed simultaneously. According to this method, Ga atoms and half of Al atoms are mixed in one atomic plane.
Al _0.33 Ga _0.67 As mixed crystal is obtained. When making an AlGaAs mixed crystal, the ratio of Al and Ga can be freely changed by changing the number of Al planes and Ga planes when making an ordered mixed crystal, and changing the ratio of TMA and TMG that flow simultaneously when making an irregular mixed crystal. You can change In addition, for doping Si, as shown in FIGS. 20 (B), (C) and 22
Instead of pulsing the silane as shown, the silane may be allowed to flow for the entire duration of the doping.

Example 7 A heterostructure compound semiconductor having the structure shown in FIG. 23 was prepared.

(100) of n-GaAs substrate 41 with carrier concentration 2 × 10 ₁₈ cm ^-3
A Si-doped Al _0.5 Ga _0.5 As mixed crystal 42 having a carrier concentration of 2 × 10 ₁₈ cm ⁻³ and a thickness of 5000 Å was formed on the surface. This can be achieved by changing the method shown in FIG. 22 so that both the TMG and TMA mole fractions are changed to 1 × 10 ⁻⁴ mole fraction and the silane concentration is changed to 1 × 10 ⁻⁶ mole fraction. Next, without introducing silane, the other conditions are the same as in FIG. 20 (B) or FIG.
An undoped Al _0.33 Ga _0.67 As layer 43, and a 20th layer
An undoped GaAs layer 44 having a thickness of 100Å is formed by the same method as shown in FIG. An undoped Al _0.33 Ga _0.67 As layer and an undoped GaAs layer are alternately formed in five layers to form a multi-quantum well layer 45. Zn-doped Al _0.5 Ga _0.5 As layer with a carrier concentration of 5 × 10 ₁₉ cm ^-3
46 is formed to a thickness of 5000 Å, and a Zn-doped GaAs layer 47 having a carrier concentration of 5 × 10 ₁₉ cm ^-3 is formed on the electrode as an electrode layer
To form. Dimethylzinc (CH ₃ ) ₂ Zn was added to TMG as Zn doping.
If the concentration of (CH ₃ ) ₂ Zn is 2 × 10 ⁷ mole fraction, it is 5 × 10 ₁₉ cm ⁻³ , and if it is 10 ⁻⁸ mole fraction, it is 2
A p-type carrier concentration of ^{x10 18} cm ^-3 is obtained.
The growth temperature is 550 ° C.

A good multi-quantum well laser can be produced by using a compound semiconductor having such a structure. That is, after forming the Ga surface, HCl
Since it introduces, there are few surface defects and deep levels,
Therefore, not only the production yield is improved, but also a laser with good light emission efficiency can be obtained. In addition, the hetero interface is sharp,
There are few defects at the interface. Furthermore, since the crystal is grown at a relatively low temperature of 550 ° C, the diffusion of Si and Zn is small. The interface having no such defects and being sharp in composition is useful for lowering the oscillation threshold current of the multi-quantum well laser in combination with good emission efficiency.

In Examples 2 to 7, the example in which trimethylgallium was used as the source gas of Ga was described, but if triethylgallium (C ₂ H ₅ ) ₃ Ga is used, the inclusion of carbon in the crystal is reduced. It's done. It is also possible to use hydrogen halide such as hydrogen iodide and hydrogen fluoride instead of hydrogen chloride.

〔The invention's effect〕

As described above, according to the present invention, it is possible to dope a III-V compound semiconductor at a high concentration.
Further, since the doping is performed by low temperature crystal growth, the diffusion of the dopant at the interface between the doped layer and the undoped layer is small. Further, a crystal having few defects can be obtained by using a method of introducing a hydrogen halide after forming an atomic plane of a group III element during crystal growth to remove surface defects and deep levels. Therefore, the method of the present invention is effective for producing high-speed FETs and multi-quantum well lasers using III-V group compound semiconductors.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used in the present invention, FIG. 2 is a time chart showing an example of a raw material gas introduction method in the present invention, FIG. 3 is a diagram showing a relationship between growth temperature and Si concentration, and FIG. FIG. 5 is a diagram showing the relationship between growth temperature and electron concentration, FIG. 5 is a diagram showing relationship between temperature, electron mobility and sheet carrier concentration, and 6 (A), (B) and (C) are FIG. 7 is a diagram illustrating the principle of the present invention, FIG. 7 is a time chart showing an example of a raw material gas introduction method, FIG. 8 is a diagram showing the relationship between the molar fraction of silane and carrier concentration, and FIG. 9 is substrate temperature. And the carrier concentration, Fig. 10 is a diagram for explaining the effect of HCl introduction, Fig. 11 is a diagram showing the relationship between growth temperature and surface defect density, and Fig. 12 is the molar content of silane. Diagram showing the relationship between the rate and carrier concentration, Fig. 13 is a time chart showing an example of the raw material gas introduction method, Fig. 14 The figure is a diagram showing the relationship between the mole fraction of silane and the sheet carrier concentration, Fig. 15 is the diagram showing the relationship between growth temperature and the sheet carrier concentration, and Figs. 16 and 17 are respectively the sheet on the doped surface. Fig. 18 is a diagram showing the carrier concentration, Fig. 18 is a sectional view showing the structure of a GaAs crystal in which a heavily doped layer is grown, and Fig. 19 is a sectional view showing the structure of a GaAs FET having a heavily doped layer, Fig. 20. (A), (B), (C) are time charts showing an example of a raw material gas introduction method for producing a doped mixed crystal hetero structure compound semiconductor, and FIG. 21 is a hetero structure compound prepared by the method of the present invention. FIG. 22 is a sectional view showing the structure of a semiconductor, FIG. 22 is a time chart showing an example of a raw material gas introduction method for manufacturing a mixed crystal compound semiconductor, and FIG. 23 is a heterostructure suitable for a multi-quantum well laser manufactured by the method of the present invention. It is a sectional view showing the structure of a compound semiconductor. . 1 ... Substrate, 2 ... Reaction tank, 3 ... Substrate support, 4 ...
Heating device, 5, 7 ... Piping, 6 ... Control device, 11 ... n-G
aAs substrate, 12 …… Si doped layer, 13 …… Au layer, 14 …… AuGeN
i layer, 21 ... Semi-insulating GaAs substrate, 22 ... n ⁺ layer, 23 ... Source electrode, 24 ... Gate electrode, 25 ... Drain electrode, 31
...... Semi-insulating substrate, 32 …… Undoped GaAs layer, 33 …… Si-doped Al _0.33 Ga _0.67 As layer, 34 …… Si-doped GaAs electrode layer, 35
...... Hetero interface, 41 …… n-GaAs substrate, 42 …… Si-doped
Al _0.5 Ga _0.5 As layer, 43 ... Undoped Al _0.33 Ga _0.67 As layer, 44
…… Undoped GaAs layer, 45 …… Multi quantum well layer, 46 …… Zn-doped Al _0.5 Ga _0.5 As layer, 47 …… Zn-doped GaAs electrode layer.

Claims (8)

[Claims] 1. A first carrier which does not react with an organometallic compound together with a hydrogen carrier gas to form a III-V group compound on a substrate.
The step of introducing the arsine diluted to a second concentration higher than the first concentration by a hydrogen carrier gas onto the substrate while constantly flowing arsine (AsH ₃ ) diluted to a concentration of The process of stopping the introduction of arsine diluted to the concentration of, and diluted with hydrogen carrier gas
In the method of forming a compound semiconductor thin film on the substrate by repeating the step of introducing an organometallic compound containing a Group III element onto the substrate, silane (SiH ₄ ) is introduced together with the organometallic compound containing the Group III element. And forming the compound semiconductor thin film by doping the compound semiconductor. 2. A first carrier which does not react with an organometallic compound together with a hydrogen carrier gas to form a III-V group compound on a substrate.
A step of introducing the hydride diluted to a second concentration higher than the first concentration by a hydrogen carrier gas onto the substrate while constantly flowing a hydride containing a group V 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 element diluted with a hydrogen carrier gas onto the substrate, and an introduction of the organometallic compound In the method of forming a compound semiconductor thin film on the substrate by repeating the process of stopping the step of introducing hydrogen halide diluted with a hydrogen carrier gas, and stopping the step, a group IV or group VI or group II together with the hydrogen carrier gas. A method of forming a compound semiconductor thin film, comprising introducing a compound containing an element onto the substrate to dope the compound semiconductor. 3. The compound semiconductor thin film formation according to claim 2, wherein the compound containing the group IV element, the group VI element or the group II element is introduced simultaneously with the organometallic compound containing the group III element. Law. 4. The method for forming a compound semiconductor thin film according to claim 2, wherein the compound containing the group IV element, the group VI element, or the group II element is introduced after the termination process of the group III element. . 5. The method according to claim 2, wherein the compound containing the group IV element, the group VI element, or the group II element is introduced subsequent to the termination process of the hydride diluted to the second concentration. A method for forming a compound semiconductor thin film as described. 6. The method for forming a compound semiconductor thin film according to claim 2, wherein the compound containing a group IV element, a group VI element, or a group II element is introduced over the entire period of each step. 7. The compound containing a group IV element is silane (Si
H ₄ ). The method for forming a compound semiconductor thin film according to any one of claims 2 to 6, wherein H ₄ ). 8. The concentration of the silane is 10 ⁻⁷ mole fraction to 10
^-3 mole fraction, Claim 7
A method for forming a compound semiconductor thin film according to the item.