JPH0434921A - Vaporpiase growth method for group iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To uniformly form an extremely thin film containing Al as a constituent element by alternately supplying a volatile organic compound having direct bond of the Al and halogen and a group V element or group V volatile compound, and using iodine as the halogen. CONSTITUTION:Material gases are supplied, for example, from an AsH3 gas bottle 9, a DEGaCl bubbler 10, a DEAlI bubbler 11, carrier H2 gas 12, and flow rates are controlled by a flowrate controller 13 and a stop valve 14. H2 gas is fed as carrier gas, a pressure in a reaction tube 1 is regulated, and a GaAs board 3 on a carbon susceptor 2 is heated by high frequency heating. After As3 is supplied into a reaction vessel 1, the AsH3 is stopped, and DEAlI is then supplied. A material no supplying time is taken, and the AsH3 is supplied. This operation is repeated. In order to prevent deterioration due to oxidation of the grown AlAs layer in the air, a thin GaAs layer as a cap layer, DEGaCl and AsH3 are likewise alternately supplied and grown, to be epitaxially grown.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for vapor phase growth of a ■-V group compound semiconductor containing Aρ as a constituent element, and in particular, a method for alternately supplying a group ■ raw material and a group V raw material. It relates to atomic layer epitaxial growth technology.

[Conventional technology]

■-Epitaxially grown layers of group V compound semiconductors are used in optical devices such as light emitting diodes and laser diodes, and in FE.
It is widely applied to high-speed devices such as T.

Furthermore, in order to improve device performance, a structure in which several to dozens of thin semiconductor layers are stacked is required.

For example, a laser diode with a quantum well structure can reduce drive current, improve temperature characteristics, and shorten wavelength.

Furthermore, FETs that utilize two-dimensional electron gas as high-speed, low-noise devices have already begun to be put to practical use at the individual level.

As a thin layer epitaxial growth method, vapor phase epitaxy (VPE method) using gas such as metal organic chemical vapor deposition method (MOCVD method) and halogen transport method has been put into practical use. Film thickness is controlled through precise control.

In addition, molecular beam epitaxial growth method (in which growth is performed by irradiating molecular or atomic beams of constituent elements in a high vacuum)
Although thickness control is relatively easy with the MBE method, precise control of molecular beam intensity, growth temperature, time, etc. is still required.

It is also possible to create a superlattice structure by continuing such precise control and alternately stacking each monoatomic layer.

However, apart from prototyping at the single-unit level, it has not been possible to integrate such thin-layer devices and produce them uniformly and with good reproducibility on large-area substrates.

As a technology to overcome this problem, atomic layer epitaxial growth (ALE) has been proposed in the Proceedings of the 16th Concave Elements and Materials Conference (T, 5untora, Extende).
d Abstract of the 16th Co.
nference on 5olid 5tate D
evices and Materials, Kobe
, 1984. PP, 647-650>.

In this method, constituent elements of a compound semiconductor or gases containing the elements are alternately supplied and adsorbed or reacted one atomic layer or one monomolecular layer at a time to grow a compound semiconductor layer of a predetermined thickness.

That is, in the case of a ■-V group compound semiconductor, the thickness of the grown film is determined by the number of repetitions of the operation of alternately supplying the group ■ and group ■ raw materials.

Furthermore, by selecting the group III raw material and optimizing the growth conditions, it is possible to keep the adsorption amount per gas supply operation constant regardless of the raw material supply partial pressure or growth temperature, making it easy to use. Multilayer thin film structures with steep interfaces at the atomic layer level can be formed.

At the same time, it has the great advantage of being able to form thin films with high uniformity due to its properties, and monoatomic layer epitaxial technology plays a major role in the integration of quantum well laser diodes, two-dimensional electron gas FETs, etc.

In atomic layer epitaxial growth, group III atoms and halogen elements, among them organometallic compounds combined with chlorine, are particularly used as group III raw materials, such as (C2H5) 2 G a C4
(diethylgallium chloride
The method using DEGaCA) allows the growth of GaAs monolayer units over the widest range of growth conditions, and because the gaseous raw material is switched by a valve and supplied to the reaction vessel, it can be grown on many large-diameter substrates at once. APL (Applied Phys.
ics Letters) vol, 52. no, 1
．． Introduced in PP, L27-29.

[Problem to be solved by the invention]

Atomic layer epitaxial technology using an organometallic compound having a bond between a group II atom and a halogen element as a group III raw material and alternately supplying this and a group V raw material has the following problems.

A is represented by A i As / Ga As.
, & as constituent elements has a large bandgap but an extremely small degree of lattice mismatch, and is indispensable for creating a good multilayer thin film structure. AjI
As an organometallic compound having a bond between AjI and a halogen element for performing atomic layer epitaxial growth of the system,
As in the case of Ga, A ll (C
2H5) 2 CJl (diethylalumin
ium chloride: D E A II C
1) has been used. However, DEAfC,e and As
In atomic layer epitaxial growth with AJIAs using H3, there are problems such as the surface of the AfflAs growth layer being rough and it being difficult to control the thickness of an extremely thin film, making it unsatisfactory as an Aρ supply source.

[Means to solve the problem]

In the vapor phase growth method of the ■-■ group compound semiconductor containing AJ as a constituent element of the present invention, a volatile organic compound having a direct bond between AJ and iodine and a group-■ element or a group-■ volatile compound are alternately grown. It is supplied onto the substrate.

[Effect]

Growth temperature in atomic layer epitaxial growth of A, RAs using DEAJCJ and AsH3 (usually 400-6
It is thought that the problem lies in the instability of AJ (11) produced by the decomposition of DEAJCjI at 00℃).In other words, AllCl undergoes a disproportionation reaction in this temperature range, and A, ff and A I C12s are generated.

3A, fCA → 2 A II + A 41 Cji
s Therefore, the metals A and R are deposited on the substrate surface without limit, and the so-called self-stop function, which is the process of coating with the Aρ compound expected in atomic layer epitaxial growth and thereby suppressing the adhesion of further A and R compounds, does not work. It will be done. This roughening of the surface causes difficulties in controlling the film thickness.

Chlorine has generally been used as a halogen that directly bonds to A and R, but other halogens such as fluorine (F), bromine (Br), and iodine (
I) is possible.

Figure 2 shows AJF, AICJI, AfflBr, and AJI.
The results of thermal equilibrium calculations and stability studies for each of I are shown below.

The initial partial pressure of monohalogenated AJ is lXl0-5~10-
'atm (7,6X10-'~7.6X10-2"l
'orr) indicates the ratio (%) of unreacted monohalogenated Ajj to the initial partial pressure after thermal equilibrium. In both cases, the proportion of unreacted monohalogenated AJ decreases at low temperatures, indicating that the disproportionation reaction is more likely to occur.

AICtl is initial partial pressure IlXl0-5at, temperature 550
At ℃, almost no disproportionation reaction occurs, almost 100%
It can be seen that AfflI exists stably.

In the atomic layer epitaxial growth of a group IV compound semiconductor containing A (as a constituent element), an organic compound in which the halogen directly bonded to AII is iodine, for example (C2H5) 2
A, RI (diet, hylaluminiu+m
fadide: DEAJI I) can be used to provide a self-stopping function.

〔Example〕

Regarding one embodiment of the present invention, a horizontal reduced pressure MOCV as shown in FIG.
This will be explained with reference to device D.

A carbon susceptor 2 is located inside a reaction vessel 1 around which a high-frequency coil 8 for heating is wound, and is supported by a susceptor holder 4.

A substrate crystal 3 is placed on the susceptor 2.

Gas is exhausted by a filter 5, an exhaust device i6, and an exhaust pipe 7.

AsH3 gas bottle 9, DEGaCA bubbler 10, DE
A, 12 A raw material gas is supplied from an I bubbler 11 and a carrier H2 gas 12, and the flow rate is controlled by a flow rate control device 13 and a stop valve 14.

In order to examine the selectivity of epitaxial growth, a 5i02 mask (not shown) can be provided on a portion of the surface of the GaAs substrate 3.

GaAs substrate 3 on carbon susceptor 2 was heated to 400 to 600 Torr by high-frequency heating by flowing H2 as a carrier gas at 9 J/sin and setting the pressure inside reaction tube 1 to 100 Torr.
Heated to 0°C. At this time, l Torr inside the reaction vessel 1
After supplying AsH3 with a partial pressure of
A, & I were supplied for 3 seconds.

After this, there is a 1-second non-supply period of raw materials, and then l To
Supply AsH3 at a partial pressure of rr for 1 second.

One second of the raw material non-supply time is sufficient time for the raw material to be removed from the reaction tube 1.

This 6 second operation was repeated 1000 times.

Furthermore, in order to prevent the grown AfIAs layer from deteriorating due to oxidation in the air, a thin GaAs layer was added as a cap layer.
DEGaCjl and AsH3 were similarly supplied alternately 200 times for growth. After the epitaxial growth, the sample was folded and cross-sectional SEM observation was performed to measure the thickness of the AJIAs layer.

FIG. 3 shows the film thickness calculated per growth when the partial pressure of DEAρI is varied at a growth temperature of 550°C.

When the partial pressure of DEAJI I is in the range of 1 to 3×1 O −2 Torr, it agrees well with the thickness of the AfflAs monolayer on the (100) plane, which is 2.83 Torr.

However, the partial pressure of DEAffl I is 3 x 10-2To
When it becomes larger than rr, the unequalization reaction becomes gradually more pronounced, and the film thickness tends to exceed the thickness of a monomolecular layer.

The lowest partial pressure at which film thickness increases due to the unequalization reaction decreases as the growth temperature decreases;
A range in which the As film thickness was equal to the monomolecular layer thickness was observed, independent of the partial pressure.

Furthermore, in a low partial pressure range where film thickness increase due to unequalization reaction does not occur, Si
No precipitation of AJAs was observed in the 02 mask portion, and selective growth was possible.

Figure 3 shows DEA! for comparison. 2. Instead of the conventional (
DEA, which is a 11-series raw material! The results using jCρ are also shown, but in this case, the film thickness of AJAs increases in proportion to the partial pressure of DEAJjcJl, and there is no tendency to be saturated with the thickness of the A, &As monolayer. remains unchanged within the growth temperature range of 400 to 600°C,
When grown in this range, A also appears on the S i 02 mask.
Precipitation of 7As was observed, and selectivity could not be obtained.

It has been shown that by using DEAjII as a raw material, ideal atomic layer epitaxial growth of AJAs can be achieved under a very wide range of conditions, and selective growth is also possible.

Furthermore, the growth of AρP and AJN without changing the type of group V elements,
The present invention can also be applied to the growth of mixed crystals including AfGaAS and the like.

In this embodiment, low pressure MOCVD was used as the vapor phase growth apparatus, but similar results can be obtained with an atmospheric pressure MOCVD apparatus or, conversely, a MOMBE apparatus that performs growth in a vacuum.

Although a compound having an ethyl group was used as the alkyl group constituting the organometallic compound of A, other organometallic compounds having an alkyl group may be used as long as they can be easily decomposed and eliminated.

As the group III raw material, As H3 was used, but in addition to hydrogen compounds, for example, As (C2H5) S (triet
(CH3) 3 AsH2 (te
tiary butylarsine: T B
A s ) may be used, or if the raw material supply rate of 0n10ff is possible, the group V metal itself may be used for heating and evaporation.

〔Effect of the invention〕

Atomic layer epitaxial growth of a ■-V group compound semiconductor containing Aff, which has a self-stopping function, as a constituent element has become possible.

A vapor phase growth method for uniformly forming an extremely thin film of a ■-V group compound semiconductor containing AjI as a constituent element has been realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a vapor phase growth apparatus used in an embodiment of the present invention, and FIG. 2 is a graph showing the reaction of epitaxial growth.
FIG. 3 is a graph showing the relationship between the raw material supply partial pressure per cycle and the grown film thickness when using DEAJ I in one embodiment of the present invention and DEAfflCJ for comparison. 1... Reaction container, 2... Carbon susceptor, 3...
- Substrate crystal, 4... Susceptor holder, 5... Filter, 6... Exhaust device, 7... Exhaust pipe, 8... High frequency induction coil, 9-A s H3 cylinder, 10...-
D E G a CII Bubbler, 11...DEAρI
Bubbler, 12...Carrier H2 gas, 13...Flow rate control device, 14...Valve.

Claims (1)

[Claims] Vapor phase growth of a III-V group compound semiconductor containing Al as a constituent element, in which a volatile organic compound having a direct bond between Al and a halogen and a group V element or a group V volatile compound are alternately supplied onto a substrate. A method for vapor phase growth of a III-V compound semiconductor, characterized in that the halogen is iodine.