JPH0782093A - Vapor phase growth method - Google Patents

Abstract

PURPOSE:To obtain an interface having high electron moving degree in good reproducibility by growing a compound semiconductor crystal layer containing In and As on a semiconductor substrate, retaining the layer at a specific temperature, then growing a semiconductor crystal layer different from the crystal layer. CONSTITUTION:A compound semiconductor crystal layer containing In and As is grown on a semiconductor substrate subjected to cleaning treatment, and then, the growth is temporally stopped and the substrate is heated to a temperature higher than a starting temperature of re-evaporation of In and the temperature is retained. Then, a semiconductor crystal layer different from the compound semiconductor containing In and As is subjected to molecular epitaxial growth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth method for growing a plurality of semiconductor crystal layers on a semiconductor substrate.
It relates improvements in the interface during the growth of the multi-layered crystal film including n _x Ga _1-x As layer.

[0002]

2. Description of the Related Art As a crystal growth method for forming an ultrathin film on a semiconductor substrate, a molecular beam epitaxial growth method has recently been noted and studied. Molecular beam epitaxial growth is
This is a method of evaporating a raw material under ultra-high vacuum and growing a target crystal on a heated substrate. As a device using the molecular beam epitaxial growth method, a high electron mobility transistor (HEMT) etc. is put to practical use. Has been done. HE
The MT uses a two-dimensional electron gas formed in the vicinity of the hetero interface between the channel layer and the electron supply layer, and it is known that the flatness and steepness of the interface greatly affect the characteristics. In a normal HEMT structure, G is used as a channel layer.
aAs and AlGaAs are used for the electron supply layer. Recently, in order to improve the performance of an ordinary lattice-matched HEMT, a pseudomorphic HEMT using lattice-mismatched InGaAs in a channel layer (hereinafter referred to as PM-HE
(Abbreviated as MT) has been developed and put into practical use. GaAs
In order to improve the flatness of the / AlGaAs interface, it is effective to suspend the growth. (M. Tanaka, Jpn. J. Appl.
Phys., 25 (1986) L155-L158).

[0003]

[Problems to be Solved by the Invention] However, PM-HEM
In the case of growth of T structure, etc., even if the growth is temporarily stopped,
The electron mobility of the grown PM-HEMT structure is low, and the reproducibility of the molecular beam epitaxial growth is H of the ordinary lattice matching system.
There was a problem that it was worse than the EMT structure.

[0004]

The present invention has solved the above problems, and an object of the present invention is to provide a vapor phase growth method capable of obtaining an interface having high electron mobility with good reproducibility. To provide. That is, in the present invention, in a vapor phase growth method for growing a plurality of semiconductor crystal layers on a semiconductor substrate, after growing a compound semiconductor crystal layer containing In and As, the growth is temporarily stopped and the substrate temperature is controlled. After the temperature is raised to a temperature equal to or higher than the re-evaporation start temperature of In and maintained, the In and A
and a semiconductor crystal layer different from a compound semiconductor containing s.

Further, the vapor phase growth method is a molecular beam epitaxial growth method, and the compound semiconductor crystal containing In and As is In _x Ga _1-x As or In _x A.
l _1-x As. As a result of intensive studies for solving the above-mentioned problems, the present inventors have thought that In segregated on the growth surface when growing an In _x Ga _1-x As layer might be the cause. By the way, In _x G
Regarding the a _1-x As layer, In is 1 on the outermost growth surface during growth.
It is known that segregation of ~ 2 atomic layers occurs.
(Proceedings of the 40th JSAP Joint Lecture Meeting No.
1, P253).

Therefore, the inventors of the present invention thought that a high quality hetero interface could be formed if the In atoms raised on the surface due to the segregation during growth could be removed. In InAs layer growth using the molecular beam epitaxial growth method (MBE method), it is known that In re-evaporation occurs at a substrate temperature of 580 to 600 ° C. However, the growth of mixed crystals containing In has a precise composition. Due to the necessity of control, the temperature is lower than this In re-evaporation temperature.

On the other hand, the substrate temperature at which Ga in GaAs is re-evaporated is 650 ° C. or higher. Therefore, In _x Ga _1-x As
If the layer growth is performed between 580 ° C. and 650 ° C., it can be expected that In floating on the surface can be removed to some extent by the re-evaporation of In, but accurate composition control of the grown In _x Ga _1-x As layer is possible. It gets harder. Therefore, the present inventor has an In _x G
a _1-x-growing As layer the substrate temperature is set below re-evaporation initiation temperature of the In perform precise composition control, In _x Ga _1-x A
After the growth of the s layer is completed, the supply of the group III source material is stopped (temporary growth is stopped), and the substrate temperature is set to the re-evaporation start temperature of In or higher (5
(80 ° C. or higher) to evaporate the excess In that has emerged due to segregation on the surface, and when the excess In disappears on the surface, the supply of Group III atoms in the next layer is started to form In at the interface. The formation of a mixed crystal with the semiconductor crystal layer grown subsequently was prevented.

[0008]

EXAMPLE Here, as an example, P is formed on a GaAs substrate.
An example of growing an M-HEMT structure is shown. Surface orientation (10
0) The layer structure shown in FIG. 1 was grown on a just GaAs substrate. In FIG. 1, 1 is Si-doped GaAs
Cap layer (film thickness 10 nm, carrier concentration 2 × 10 ¹⁸ c
m ^-3 ), 2 is an Si-doped AlGaAs electron supply layer (film thickness 10 nm, carrier concentration 2 × 10 ¹⁸ cm ^-3 , Al composition 0.24), 3 is an undoped AlGaAs spacer layer (film thickness 2 nm, Al composition 0. 24) and 4 are undoped I
nGaAs channel layer (film thickness 10 nm, In composition 0.
15) and 5 are undoped GaAs buffer layers (film thickness 50
0 nm) and 6 represent an undoped GaAs substrate ((100) just). The vapor phase growth apparatus is an ordinary solid source M
A BE device was used. First, cleaning was performed at 640 ° C. for 15 minutes as a cleaning treatment of the GaAs substrate before the start of growth.

Next, after growing undoped GaAs as a buffer layer on the GaAs substrate by 0.5 μm at a substrate temperature of 600 ° C., the substrate temperature is lowered to 530 ° C. and In ₀₁₅ Ga _{085 is obtained.}
The As layer was grown to 180 nm. After the growth of the In ₀₁₅ Ga ₀₈₅ As layer, the supply of In and Ga was stopped (temporary stop of growth), and at the same time, the substrate temperature was raised to 600 ° C. and held for 1 minute, and then the next Al ₀₂₄ Ga ₀₇₆ As layer was formed. grown. In
After the growth of ₀₁₅ Ga ₀₈₅ As layer, shows a change in timing and the substrate temperature of the raw material supply switching to the next Al ₀₂₄ Ga ₀₇₆ As layer grown FIG.

The grown epitaxial layer is at room temperature and 77
The Hall measurement at K was used to evaluate the concentration and mobility of the two-dimensional electron gas. In addition, AlGaAs / InGaAs /
As the evaluation of the interface of the single quantum well of GaAs, the photoluminescence (PL) measurement at 77K was performed and the half width thereof was obtained. The results are shown in Table 1. For comparison, in Comparative Example 1, the growth was temporarily stopped for 1 minute and the substrate temperature was not changed, and in Comparative Example 2, the growth was not temporarily stopped, and the growth of the InGaAs layer was followed by A.
Table 1 also shows the results of similar evaluations for the case where the 1GaAs layer was grown.

[0011]

[Table 1] Although there is no difference in the two-dimensional electron gas concentration and the mobility between Comparative Examples 1 and 2, Comparative Example 1 is obtained by the PL measurement at 77K.
The half-width has become smaller due to the effect of the suspension of growth. In the example of the present invention, the mobility at room temperature and 77K is higher than that in the comparative example, and the PL half-value width at 77K is also 25.9 meV.
It can be seen that a high quality AlGaAs / InGaAs interface can be formed by the effect of temporarily stopping the growth and raising / holding the substrate temperature to the re-evaporation start temperature of In or higher. In the embodiment, since the layer grown after the InGaAs layer is AlGaAs, the substrate temperature is not changed after the growth is temporarily stopped, but the substrate temperature may be changed again depending on the growing crystal.

Further, in the embodiment, the time for keeping the substrate temperature at the re-evaporation start temperature of In or higher is set to 1 minute, but it is not limited to this and can be appropriately selected, and is usually about 1 to 3 minutes. . Further, in the embodiment, the example of the InGaAs layer is shown, but it is needless to say that it can be applied to the InAlAs layer.

[0013]

As described above, according to the present invention, the growth is temporarily stopped and the substrate temperature is set to I during the temporary stop of the growth.
By elevating the temperature above the re-evaporation start temperature of n to re-evaporate excess In, it became possible to form a good interface with excellent steepness.

[Brief description of drawings]

FIG. 1 is a diagram showing a layer structure of an epitaxial layer of an example.

FIG. 2 is a diagram showing a timing of supply of raw material and changes in substrate temperature according to the present invention.

[Explanation of symbols]

 1. Si-doped GaAs cap layer 1. Si-doped AlGaAs electron supply layer 3. Undoped AlGaAs spacer layer 4. Undoped InGaAs channel layer 5. Undoped GaAs buffer layer 6. Undoped GaAs substrate

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[Procedure amendment]

[Submission date] August 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Next, after growing undoped GaAs as a buffer layer on the GaAs substrate by 0.5 μm at a substrate temperature of 600 ° C., the substrate temperature is lowered to 530 ° C. and In _0.15 G
An a _0.85 As layer was grown to 180 nm. In _0.15
After the growth of the Ga _0.85 As layer, the supply of In and Ga was stopped (temporarily stopped the growth), and at the same time, the substrate temperature was raised to 600 ° C. and kept for 1 minute, and then the next Al _0.24 Ga was added.
_{A 0.76} As layer was grown. In _0.15 Ga _0.85
FIG. 2 shows the timing of switching the raw material supply and the change in the substrate temperature after the growth of the As layer until the next growth of the Al _0.24 Ga _0.76 As layer.

Claims (3)

[Claims] 1. A vapor phase growth method for growing a plurality of semiconductor crystal layers on a semiconductor substrate, wherein after growing a compound semiconductor crystal layer containing In and As, the growth is temporarily stopped,
A vapor-phase growth method, comprising: raising a substrate temperature to a temperature equal to or higher than a re-evaporation start temperature of In and holding the substrate temperature; and then growing a semiconductor crystal layer different from a compound semiconductor containing the In and As. 2. The vapor phase growth method according to claim 1, wherein the vapor phase growth method is a molecular beam epitaxial growth method. 3. The gas phase according to claim 1, wherein the compound semiconductor crystal containing In and As is In _x Ga _1-x As or In _x Al _1-x As. How to grow.