JPS6211221A - Molecular-beam epitaxial growth method - Google Patents

Abstract

PURPOSE:To form a GaAs epitaxial film having high quality by irradiating a substrate by As and In molecular beams in a substrate-surface purification process before growth, growing an InxGa1-xAs buffer layer and growing GaAs onto the In-doped GaAs substrate. CONSTITUTION:The upper section of an In-doped GaAs substrate 1 is irradiated by As molecular beams and In molecular beams in a substrate purification process to grow an InxGa1-xAs buffer layer 2. A value corresponding to the In concentration (x-0.002) of the substrate 1 is used on the starting of the growth of (x), (x) is reduced gradually with growth, (x) is brought to 0, and a GaAs layer 3 is grown. Accordingly, a GaAs epitaxial film having low dislocation density and of high quality is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a molecular beam epitaxial growth method for growing GaAs on an In doped GaAs substrate by molecular beam epitaxial growth.

<Conventional technology> Ga is grown by molecular beam epitaxial growth (hereinafter referred to as MBE).
When growing GaAs on an As substrate, the conventional method is as follows. That is, the GaAs substrate is transported into a growth chamber after being chemically treated. Then under high vacuum
The substrate was irradiated with only the s molecular beam at 600~6
By heating to 50° C., the natural oxide film and deposits such as carbon on the substrate surface are removed and the substrate surface is cleaned (substrate surface thermal cleaning process). After that, Ga and As molecular beams were applied at 500
By irradiating the substrate kept at ~700°C, GaA
s growth.

By the way, the substrate used for growth in the conventional method is undoped G.
aAs substrate or Cr with low vapor pressure attached n1-7+
("!r)-fu" G a A M Z Layer Power; The Lord was there.

However, "In-doped GaAs substrates have recently attracted attention for their ability to obtain low dislocation density or dislocation-free crystals, and if this is used as an epitaxial growth substrate, it is thought that high-quality epitaxial films with low dislocation densities can be grown." .

<Problem to be solved by the invention> However, according to the conventional method, Indo'7"G a
When GaAs is grown on an s-substrate, the following problems occur.

■ When the substrate temperature is over 500℃, only As is removed from the substrate.
Because In also selectively evaporates, the conventional method of irradiating the substrate with only As molecular beams during the substrate surface thermal cleaning process
evaporates from the substrate, which deteriorates the surface morphology of the growth interface and deteriorates the quality of the GaAs film grown thereon.

■ In-doped GaAs is actually a mixed crystal InxGa
Since it is s-xAs(x-0,002), it is undoped and St.

The lattice constant is approximately 0.02% larger than that of Sn-doped (n-type) or Be, Mg-doped (P-type) GaAs. Therefore, when undoped GaAs or the like is grown on an In-doped GaAs substrate, internal stress is generated at the interface due to lattice mismatch, which may cause dislocations in the grown layer, making it impossible to obtain a good quality epitaxial film.

The present invention was devised in view of the above points, and an object of the present invention is to provide a molecular beam epitaxial growth method that makes it possible to form a high quality GaAs epitaxial film on an In doped substrate.

Means for Solving the Problems> In order to achieve the above object, the In-doped GaA of the present invention
The molecular beam epitaxial growth method for growing GaAs onto an s-substrate is constructed as follows.

(2) In the substrate surface thermal cleaning process, the substrate is irradiated not only with As molecular beams but also with In molecular beams of, for example, about 10-10 to 10-'torr, to compensate for the evaporation of jn from the substrate.

■ Growth is preceded by GaAs growth, first InxGa,
-XAs, for example, from 0.01 to 5. Grow i<m.

As an example, the value of X is a value corresponding to the In concentration of the In-doped GaAs substrate at the start of growth (X ~ 0.002
) and change X to O with growth 5, then G
Grow aAs.

Effects> The configuration (2) above provides a clean surface and good surface morphology required for high-quality epitaxial production. Further, according to the configuration (2) above, a mixed crystal InxGa, -xAs having a lattice constant value between that of the In doped GaAs substrate and the GaAs film grown thereon is grown as a buffer layer, and as an example, this By changing the lattice constant by changing the value continuously or stepwise, it is possible to eliminate the lattice mismatch that occurs between the substrate and the epitaxially grown layer.

<Example> The present invention will be described in detail below based on an example with reference to the drawings.

FIG. 1 is a cross-sectional view showing the structure of a semiconductor device manufactured according to the present invention.

In the figure, 1 is an In-doped GaAs substrate, 2 is an I
nxGa + -xA s buffer layer, mixed crystal ratio X
The profile is a value corresponding to the In concentration of the substrate 1 at the interface with the substrate 1, and is configured to become O as the buffer layer 2 grows. Further, 3 is a GaAs layer.

Next, a method for manufacturing a semiconductor device having the structure shown in FIG. 1 as an embodiment of the present invention will be described.

The substrate 1 used was a commercially available In-doped semi-insulating (1
00) A 2" wafer of a substrate (thickness: 400 gm) has an In concentration of about 1X10 (equivalent to 0.004 GaO, 996 As). Growth was performed by direct heating using an In-free susceptor.

Surface cleaning was performed using As molecular beam 2 x I at a substrate temperature of 620°C.
F'torr, In molecular beam I X 10-9t
The test was carried out by irradiating the substrate 1 with orr. After about 30 minutes, surface cleaning was confirmed using a RHEED (reflection high energy electron diffraction) device in the growth chamber, and then the growth shown in FIG. 1 was carried out.

The growth conditions were a substrate temperature of 580°C and a growth rate of 0.7 μm/
I did it with h. First, the buffer layer shown in FIG.
In order to grow xGa1 and As layer 2, the Ga molecular beam intensity was kept constant at 3.2 x 10-' torr, the As molecular beam intensity was kept constant at I x 10 torr, and the In molecular beam intensity was set at 7 at the start of growth of buffer layer 2. X I F"to
The buffer layer Inx has a mixed crystal ratio profile in which the mixed crystal ratio X continuously changes from 0.004 to O by setting the ratio to
Ga and XAs were grown to a thickness of 0.2)1 m. After this, Si
Doped n-type GaAs layer 3. (Carrier concentration lXl0
3) was grown to 17 m.

As a result, the GaAs layer 3 reflects the low dislocation density of the substrate 1.
The dislocation density was about 1ooo--3. In addition, the carrier concentration is 1015 cR-3 and the mobility is 8000 r”s.
A good value of eQ was obtained.

<Effects of the Invention> As described above, according to the present invention! 17. In-doped GaAs
It is now possible to form a high-quality GaAs epitaxial film with a low dislocation density by taking advantage of the low dislocation density characteristic of the substrate, and by using this as an epitaxial film for 0EIC and HBT, it is possible to manufacture high-performance and highly reliable ICs and transistors. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a semiconductor device manufactured according to the present invention. 1.=I n-doped GaAs substrate, 2-=I
nxGa, -xAs buffer layer, 3...GaA
s layer. Agent Patent attorney Aihiko Fuku (2 others) 1st FFI -3-5 layer, 21nzGa1. zAs grainyy) @ −/ InF-y°GaA溗1hi ■

Claims (1)

[Claims] 1. In the molecular beam epitaxial growth of GaAs on an In-doped GaAs substrate, the substrate is irradiated with an As molecular beam and an In molecular beam in the substrate surface thermal cleaning process before growth, and then the GaAs is grown. mixed crystal In_xGa_1_-_
A molecular beam epitaxial growth method characterized by growing xAs as a buffer layer and then growing GaAs on an In-doped GaAs substrate. 2. In_xGa_1 formed as the buffer layer
_-_xAs is a patent characterized in that at the substrate interface, the mixed crystal ratio x has a value corresponding to the In concentration of the substrate, and as it grows, x decreases and finally has a mixed crystal ratio profile where x = 0. The molecular beam epitaxial growth method according to claim 1.