JPH01313927A - Compound-semiconductor crystal growth method - Google Patents

Abstract

PURPOSE:To enable a compound semiconductor crystal to grow at a temperature lower than conventional devices, and to improve the performance of a device using a hetero-junction by employing a phenyl compound of a constituent component making up the compound semiconductor crystal as at least one kind of a raw material gas. CONSTITUTION:(C6H5)3Ga (triphenylgallium; TPG) is used in place of (CH3)3Ga (trimethylgallium; TMG) and (C2H5)3Ga (triethylgallium; TEG) and the like which have been employed as a gaseous raw material substance in a conventional atomic layer epitaxy method. TPG has a group having molecular weight higher than TMG and TEG, and is decomposed at a comparatively low temperature. Accordingly, crystal growth through the atomic layer epitaxy method can progress at a low temperature, a hetero-interface having steep band structure and an impurity distribution profile can be formed, and the performance of a device can be improved.

Description

[Detailed Description of the Invention] [Summary] This invention relates to the growth of compound semiconductor crystals by a vapor phase growth method called atomic layer epitaxy.

The aim is to make it possible to grow compound semiconductor crystals at lower temperatures than before.

It is constructed by using a phenyl compound, which is a component element constituting the compound semiconductor crystal, as at least one kind of source gas for growing the desired compound semiconductor crystal.

[Industrial application field]

The present invention relates to a method for growing compound semiconductor crystals by vapor phase growth, and in particular to a growth method called atomic layer epitaxy in which component source gases are alternately introduced into a vapor phase growth apparatus to grow compound semiconductor crystals. .

[Conventional technology]

In the atomic layer epitaxy method, gaseous raw materials containing individual component elements constituting a compound semiconductor crystal are alternately introduced into a vapor phase growth apparatus, and this process is repeated to grow a compound semiconductor crystal. GaAs
Taking crystals as an example, gaseous raw materials containing Ga and As, respectively.

For example, (CHs)sGa ()limethylgallium) and A
sH3 (arsine) is alternately introduced into the vapor phase growth apparatus.

Each raw material is adsorbed onto the substrate and then thermally decomposed to form a monoatomic layer of each component element, so a monomolecular layer of GaAs is generated every cycle of introduction of the raw material. Therefore, it is possible to control the desired compound semiconductor crystal and the impurities added to it on an atomic layer basis, and the bimolecular beam epitaxy method is a means to realize electronic devices with functions that cannot be obtained with conventional bulk materials. It is expected that

In the conventional metal organic chemical vapor deposition (MOCVD) method in which source gases are simultaneously introduced into a vapor phase growth apparatus, it is necessary to maintain the substrate temperature at 650° C. to 700° C. during crystal growth. On the other hand, according to the atomic layer epitaxy method, 5
Compound semiconductor crystals can be grown at a substrate temperature of about 0.000C. Lowering the growth temperature of compound semiconductor crystals is important for improving the performance of devices using heterojunctions because it can sharpen the band structure and impurity distribution profile at the heterointerface of different compound semiconductors.

[Problem to be solved by the invention]

However, when the growth temperature becomes about 500°C.

Interdiffusion of atoms constituting a compound semiconductor crystal and diffusion of impurity atoms occur, making it difficult to form a steep heterointerface and control the impurity distribution profile with the precision of a monoatomic layer. Furthermore, when a heterointerface made of compound semiconductor crystals having significantly different coefficients of thermal expansion is formed, the compound semiconductor crystals are greatly warped and distorted when the heterointerface is cooled to room temperature.

An object of the present invention is to solve the above problems by making it possible to grow compound semiconductor crystals at lower temperatures than conventional ones.

[Means to solve the problem]

The above-mentioned object is to grow a desired compound semiconductor crystal by an atomic layer epitaxy method using a small amount of raw material gas (the present invention is characterized by using a phenyl compound as a component element constituting the compound semiconductor crystal as one type). This is achieved by such a compound semiconductor crystal growth method.

[For production]

For example, instead of (CHz):iGa ()trimethylgallium, TMG) and (CHs)zGa ()ethylgallium; TEG), which were used as gaseous raw materials in the conventional atomic layer epitaxy method, C4
H6) zGa (triphenylgallium, TPG
) is used. TPG has a group with a larger molecular weight than Tl'lG and TEG.

Decomposes at relatively low temperatures. As a result, crystal growth by atomic layer epitaxy can proceed at low temperatures.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an elevational view showing the general configuration of the vapor phase growth system used in the implementation of the present invention.Inside the vapor phase growth apparatus 1 made of, for example, a quartz tube, there is provided a support mechanism 2 with low thermal conductivity. a supported 9 susceptor 3 made of graphite, for example;
is provided.

A compound semiconductor crystal is formed at one end of the susceptor 3. A substrate 4 made of GaAs single crystal or the like is fixed. A high frequency heating device 10 for heating the susceptor 3 is provided outside the vapor phase growth device 1 .

At one end of the vapor phase growth apparatus 1, an exhaust pipe 5 is provided which is connected to a vacuum evacuation equipment (not shown).

Through this, the inside of the vapor phase growth apparatus 1 can be evacuated to a vacuum. A manifold 6 is provided at the other end of the vapor phase growth apparatus 1, and hydrogen gas (Hz) is supplied through gas switching valves 7.8 and 9 connected to this manifold 6.
), As11. , and (C6H5) 3Ga are introduced, respectively.

While controlling the temperature of the susceptor 3 and maintaining the substrate 4 temperature at 250°C, the gas switching valve 7.8°9 is alternately switched to 112° (C6H5) in the vapor phase growth apparatus 1.
zGa and A s fl 3 were introduced alternately at the flow rates and times shown in the table below.

Hz (CJs)iGa Hz AsH3 stylet
l(SCCM) 500 x 500
480 hours (seconds) 3 10 3
10+ (Cbbs)3Ga was introduced into a bubbler maintained at 54°C by flowing H2 as a carrier at a flow rate.

H2 in the above table is + (Ci+H5)3Ga and A
This gas is introduced to purge residual gas in the vapor phase growth apparatus 1 while sH is alternately introduced. Also,
In order to eliminate pressure fluctuations when introducing (C,Hs)3'Ga and ASH:l, an appropriate amount of H2 is added to these gases to maintain the total flow rate at a constant value.

The thickness of the GaAs crystal grown on the substrate 4 by repeating 2, for example, 177 cycles with the above conditions as one cycle (C6H
5) The relationship with 3Ga flow rate (x) is shown in Figure 1.

The vertical axis in the figure represents the average growth thickness per period expressed in terms of the number of molecular layers of GaAs crystal.

According to Figure 1, the flow rate of (Ci, Hs) 3Ga is 20
When reaching 05CCH, the GaAs crystal is
It has been shown that growth occurs one molecular layer at a time, and that even if the amount of sludge is increased further, the growth thickness per cycle does not increase. Furthermore, it can be seen that when the flow rate of (C6H5) and Ga is 2005 CCM or less, one molecular layer does not grow in each period.

In the above, the above T used in the conventional atomic layer epitaxy method instead of + (C611s) 3Ga
Although an attempt was made to grow a GaAs crystal by introducing a raw material gas such as MG or TEG, no growth was observed at a substrate temperature of 250°C to 300°C. Thermal decomposition of these TMG and TEG was insufficient and growth did not proceed.

As mentioned above, as a raw material gas for Ga (CJS) z
It was shown that atomic layer epitaxy growth at 250° C. is possible by using Ga.

The above reduction in the growth temperature is estimated as follows. That is, + (C3I%): +Ga is (C, tls) on the heated substrate surface, Ga (n = 1 to 3)
Adsorbs in the form of Compared to the CH3 group in TMG and the C21 group in THE, the C, H, group has a weaker bonding force to Ga atoms, so even at low temperatures below 250°C, they easily decompose on the substrate surface and form a Ga monoatomic layer. As T
MG and TME are insufficiently decomposed at such low temperatures, and crystal growth does not proceed.

Although the above example shows the case where GaAs crystal is grown by atomic layer epitaxy, other compound semiconductor crystals such as AlAs can also be grown by using phenyl compound of AI as the source gas instead of conventional TMA. It is clear that a reduction in growth temperature is possible.

In addition, since a vaporizable raw material having a large molecular weight group such as TPG is extremely difficult to obtain at present, the present invention is limited to TPG, but the idea of the present invention is that it has the same effect as TPG. Needless to say, this applies to other raw materials as well.

〔Effect of the invention〕

According to the present invention, a compound semiconductor crystal can be grown at a lower temperature than conventional methods by atomic layer epitaxy, and a heterointerface having a steep band structure and impurity distribution profile can be formed.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the flow rate of triphenylgallium and the average growth thickness of GaAs crystal per period in the growth method of the present invention. FIG. 2 is an elevational view showing the general configuration of a vapor phase growth system used to carry out the growth method of the present invention. In fig. 1 is a vapor phase growth device. 2 is a support mechanism. 3 is the susceptor. 4 is the board. 5 is the exhaust pipe. 6 is the manifold. 7, 8 and 9 are gas switching valves. 10 is a high frequency heating device. Fig.1

Claims (1)

[Claims] While heating a substrate on which a desired compound semiconductor crystal is to be formed to a predetermined temperature in a vapor phase growth apparatus, a gaseous substance containing each of the component elements constituting the compound semiconductor singly is placed in the vapor phase growth apparatus. A method for growing compound semiconductor crystals on the substrate by alternately introducing gaseous substances, wherein at least one of the gaseous substances is a phenyl compound of the component element.