JPH0459699A - Production of longitudinal semiconductor superlattice - Google Patents

Abstract

PURPOSE:To reproducibly and uniformly obtain the subject longitudinal semiconductor superlattice by alternately supplying raw material gases respectively containing an element constituting a semiconductor crystal layer to a base plate for growth. CONSTITUTION:A respectively prescribed amount of trimethylgallium and trimethylaluminium are initially alternately supplied onto a GaAs base plate 11 in order and Al and Ga atom planes are grown on a terrace 11a of the base plate crystal surface in the lateral direction to the step. Arsine (AsH3) is then supplied thereto to grow GaAs:15 and AlAs:14. According to the above- mentioned method, AlAs and GaAs are grown in order and a longitudinal superlattice is formed. As a single atom layer growth method where raw materials are alternately supplied is used in the above-mentioned method, deposition of Al on the next terrace can entirely be prevented in growth of GaAs on the remaining terrace part without requirement of accurate control of the growth conditions such as the supply of trimethylgallium, the growth pressure and the growth temperature. An ideal longitudinal superlattice can be formed therefor.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a method for manufacturing a vertical semiconductor superlattice used in a one-dimensional transistor or a low oscillation threshold laser having a quantum well thin wire structure. Regarding.

(Prior art) In addition to the potential V (Z) in the growth direction of a conventional superlattice (two-dimensional superlattice), by adding an artificial potential V (x + y) in the in-plane direction, quantum wire It has been pointed out that if a structure such as et al., Jpn, J, App
I, Phys, 28 L, 31.4 (1989)
).

The most promising method for creating fine synchronous structures in the growth plane is to deposit GaAs and AQAs alternately on periodic atomic steps on the off-substrate surface with misorientation (P, M .

Petroff et al., Appl, Phys, Lett
, 45620 (+984)), in this method, the period Lx in the in-plane direction is the average terrace length aXcotα (where a is the thickness of one semiconductor molecule layer, 2.83, and α is the off-angle).
is given by Recently, a planar superlattice structure with a periodic structure on the order of 100 nanometers has been produced by this method using MBE (Molecular Beam Epitaxial Method) (J, M, Ga1nes et al., J, Vac, Sci & Technol, 8).
6°1378 (+988)) and MOCVD (Metalorganic Chemical Vapor Phase Deposition) (T, Fukui, Appl.
Phys, Lett 50. ,! 124 (19
87)). However, when growing a vertical superlattice by conventional MBE or MOCVD, the growth rate is lowered and the amount of growth when multiple semiconductor layers forming the superlattice are grown alternately is precisely equivalent to one molecular layer. The amount needs to be controlled. . It is said that even if the growth amount deviates slightly from the amount equivalent to one molecular layer, the vertical superlattice tilts significantly. For example, taking a vertical superlattice made of iAs and GaAs as an example, if the tilt angle of the vertical superlattice is β and the tilt angle of the substrate is θ, then tanβ=(1−(m
+ n ))/lan fj holds true. Here m and n
are the exponents m and n of (AQAs)m(6aAs)n. Therefore, when m+n=1, that is, exactly one molecular layer of AQ, A is spread over the entire surface of the terrace without overflowing to the adjacent terrace.
When s and GaAs are grown, β=0 degrees. However, for example, if θ=2° and m+n= ], 05, then β#55
It also becomes °. m+n=1.05 is 5, for example Ga
This corresponds to the case where one As molecule is deposited onto the next terrace.

In order to control the structure of a vertical superlattice by conventional MBE or MOCVD, it is necessary to precisely control the growth time and the amount of raw material supplied. However, in MBE, in order to suppress precipitation on the next terrace and to grow different semiconductor layers one molecular layer sequentially over the entire terrace surface, it is necessary to control the temperature of the Knudsen cell filled with the source.
In CVD, there are difficulties in controlling the flow rate of raw materials. As described above, although it is not impossible using conventional techniques, there is a problem in that it is difficult to produce a vertical superlattice with good reproducibility.

(Problems to be Solved by the Invention) In order to form a vertical superlattice using the above-mentioned conventional MBE method and MOCVD method, the amount of raw material supplied must be controlled with high precision, and the Moreover, there is a problem in that it is difficult to uniformly grow a vertical superlattice over the entire surface of a 2-inch wafer, for example.

It is an object of the present invention to provide an improved method for creating a vertical superlattice in view of the problems of the conventional growth methods described above.

[Structure of the invention]

(Means for Solving the Problems) A method for manufacturing a vertical semiconductor superlattice according to the present invention is such that the index plane of the crystal is (100), (I ], I ),
Or, when a vertical semiconductor superlattice is formed by arranging a substrate tilted in a predetermined direction from (110), etc., and growing two or more types of semiconductor crystal layers in monolayer sequentially on the crystal plane,
The method is characterized in that raw material scraps containing constituent elements of a single conductor crystal layer are alternately introduced into a growth container to form a semiconductor superlattice on the crystal plane of the substrate by a single atomic layer growth method.

(Function) According to the present invention, by alternately supplying raw material gas onto the growth substrate, a vertical semiconductor superlattice can be uniformly produced on the growth substrate with good reproducibility.

The operation of the present invention will be explained using a GaAs/AQAs vertical superlattice as an example with reference to FIG.

First, a GaAs (100) 2°off substrate (off
A certain amount of trimethyl gallium (TMG) and trimethyl aluminum (TMA) are sequentially and alternately supplied in the direction (110)) 11, and AQ and Ga atomic planes are formed laterally from a step on the terrace portion 11a of the substrate crystal surface. grow (Fig. 1(a)).

Next, arsine (ASHJ) is supplied to grow GaAs15 and AQAs14 (FIG. 1(b)). By growing ρAs and GaAs sequentially as described above, a vertical superlattice as shown in FIG. 1(b) is created. Monoatomic layer growth method (Atomj, c Laye) in which raw materials are alternately supplied
r Epitaxy) %, for example, in Figure 1 (
As shown in b), when growing GaAs on the remaining terraces, AQ can be deposited on the next terrace without accurately controlling the growth conditions such as TMG supply amount, growth pressure, and growth temperature. This makes it possible to create an idealized vertical superlattice as shown in FIG. 1(b). In this way, it is possible to create an ideal vertical superlattice, which has been difficult to create using conventional growth methods.

(Example) As an example of the present invention, GaA on an inclined substrate will be described below.
The fabrication of the s/AQAs vertical superlattice will be explained with reference to FIGS. 1 and 2. The substrate is GaAs (100)
A 2°-off substrate 11 was used. The off direction is ((111)
It is. Trimethylgallium (TMG) is used as the GaK material, trimethylaluminum (TMA) is used as the AQ material,
Arsine (AsH, ) was used as the As raw material. Growth container] 02 is equipped with a substrate 11 placed on a susceptor 103, and high-frequency heating is performed by a heating coil 105 to heat treat the surface and grow GaAs in the buffer layer at a growth temperature of 650.
After growth at .degree. C., the growth temperature is set at 500.degree. C., and 1.2 .mu.mol of TMA is introduced from the gas inlet 104 using hydrogen as a carrier gas. Thereafter, after performing H2 substitution, 0.3 μmol μm of TMG is introduced from the gas inlet 104. Next, after performing H2 replacement, 150 μmol of AsH is introduced from the waste inlet 104 using H2 as a carrier gas, and then H2 replacement is performed. This growth process 1
Growth was performed for 1800 cycles. 1
The cycle is: NA introduction/H2 substitution/TM
This corresponds to six waste introduction processes: G introduction/H2 substitution/AsH3 introduction/H2 substitution. In addition, the growth pressure is 3
It was set to Torr. The inside of the growth container 102 was evacuated from the gas exhaust port 106 to meet the above set conditions.

The thickness of the thin film crystal grown in this manner was about 5100, and the film thickness grown per cycle was equivalent to one molecular layer. Also, from the diffraction angle of the superlattice obtained from X-ray diffraction,
The superlattice period matched the atomic step spacing. Furthermore, it was confirmed from TEM [l] that an idealized vertical superlattice with no tilt was created. In this example, an example of creating a vertical superlattice of 0.5 molecules of GaAs and 0.5 molecules of -4QAs is shown.
By changing the amount of A supplied, a vertical superlattice of m molecular layers of GaAs and n molecular layers of AQAs (m+n=1) can be created. Furthermore, in this example, two types of semiconductor layers were grown alternately while forming one molecular layer, but three or more types of semiconductors were grown sequentially by a monoatomic layer growth method.
It is also possible to form a vertical superlattice consisting of three or more types of semiconductors.

〔Effect of the invention〕

In the method for manufacturing a vertical semiconductor superlattice according to the present invention, two or more kinds of crystals are formed on a substrate crystal surface whose index plane of the crystal is tilted in a predetermined direction from (1,00), (111), or (]10), etc. When a male semiconductor superlattice is created by sequentially growing monomolecular layers of semiconductor crystal layers, a source gas containing the constituent elements of the semiconductor layer is alternately supplied onto the substrate to be grown. There is a remarkable effect that a vertical semiconductor superlattice can be manufactured in a good and uniform manner.

[Brief explanation of the drawing]

1(a) and 1(b) are diagrams for explaining the present invention in detail, FIG. 2 is a diagram showing essential parts of a vapor phase growth apparatus used in one embodiment of the present invention, The figure is a diagram for explaining the tilt angle β of a vertical superlattice. 11.GaAs substrate, lla...Trace of substrate, 12
-GaAs, 13-AQAso (b) Agent Patent Attorney Norio Ogo 74: AQAS 15:GaAs Fig. 1

Claims (1)

[Claims] The index planes of the crystal are (100), (111),
Alternatively, when a vertical semiconductor superlattice is formed by arranging a substrate tilted in a predetermined direction from (110) and growing two or more types of semiconductor crystal layers in monolayer sequentially on the crystal plane, 1. A method for producing a vertical semiconductor superlattice, characterized by forming a semiconductor superlattice on the crystal plane of the substrate by a monoatomic layer growth method by alternately introducing raw material gases containing constituent elements into a growth container.