JPS6119120A - Manufacture of compound semiconductor substrate - Google Patents

Abstract

PURPOSE:To provide the interfaces between growing layers comprising different compositions with excellent steepness by a method wherein the growing speed is controlled by means of changing flow rate of organic and metallic gas while keeping the overall gas flow rate in a reactor constant. CONSTITUTION:An n type GaAs substrate 31 is placed on a susceptor to produce a compound semiconductor substrate by means of heating the susceptor using high frequency coils 3. In such a production process, layer growing speed may be controlled by means of reducing the flow rate of organic and metallic gas and AsH3 gas to decelerate the epitaxial growing speed while keeping the overall gas flow rate constant near the interfaces between growing layers comprising different compositions i.e. between an n type GaAs buffer layer 32 and an n type Ga1-xAlxAs clad layer 33 as well as between a p type Ga1-xAlxAs clad layer 35 and a p type GaAs cap layer 36 etc. Through these procedures, the interfaces between growing layers may be provided with excellent steepness. Besides as for the substrate 31, II-VI group compound semiconductor substrates may be applicable in addition to GaAs substrates (III-V groups).

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a compound semiconductor substrate, and in particular -
The present invention relates to a method of manufacturing a compound semiconductor substrate by performing an epitaxial thin film growth method on a V group or ■-■ group compound semiconductor substrate.

[Technical background of the invention and its problems]

As is well known (III-V group such as GaAs or ■
-The epitaxial growth method for group compound semiconductor substrates includes:
Liquid phase epitaxy (LPE) method, hydride vapor phase epitaxy (VPE)
) method, metal organic pyrolysis (MOCVD) method, and molecular beam epitaxial (MI3E) method.

Among these, MOCVD method has good in-plane film thickness uniformity,
This method is expected to be widely used in the future due to its good thin film controllability, ease of multilayer growth, and ease of mass production.

Conventionally, as a growth apparatus for performing the MOCVD method, for example, the one shown in FIG. 2 is known. 1 in the figure is a cylindrical bell jar. Inside this bell jar 1, for example, G.
A susceptor 2 for installing an aAs substrate is provided, and a high frequency coil 3 is wound around the bell jar 1. This coil 3 heats the susceptor 2 to several hundred degrees. The bell jar 1 contains trimethyl gallium (TMG).
), a first container 4 containing trimethylaluminum (TMA), a second container 5 containing trimethylaluminum (TMA), and a third container 6 containing diethylzinc (DEZ) are communicated through each pulp. There is. In addition, 7 in the figure is A II Hz
7H2 gas, 8 a2se, 12 gas, and 9 H2 gas, respectively. Further, 10 to 16 in the figure indicate mass flow controllers that control the flow rates of each gas, and 17 to 27 indicate air-operated pulps.

Using a device with such a structure, GaAtAs shown in FIG.
A double heterostructure compound semiconductor substrate having a /GaAs epitaxial crystal film is manufactured as follows. First, place 3 GaAs substrates on the susceptor 2,
The susceptor 2 is heated to several hundred degrees by the high frequency coil 3. Here, in the bell jar 1, initially a certain amount of several percent of Af
iH,/' While flowing H2 gas 7 and H2 gas 9, when the susceptor temperature reaches the set value, the first container 4 is
Then, TMG is bubbled with H2 gas, the vaporized gas is drawn into the bell jar 1, and an n-type GaAs buffer layer 32 is formed.
grow. Note that the initial path of the H2 gas 9 passes through the controller 13 and the pulp 2 in this order. Furthermore, when supplying vaporized gas, the H2 gas 9 enters the first container 4 via the controller 14 and the valve 23;
, through valve 20.

Next, the TMG line is closed while leaving the H2 gas and AmHs gas lines as they are. And TMG and TM
Set the flow rate of A to a flow rate corresponding to the composition ratio and then turn T again.
MG and TMA are drawn into the bell jar 1 with a valve of H2 gas, and the n-type Ga, -XA-1XAII, and Do layers 3
Grow 3. At this time, one path of the H2 gas 9 enters the first container 4 via the controller 14 and the valve 23.
The vaporized gas passes through valve 22.20. Also, H2 gas 9
The other route is through the controller 15 and the valve 25, and then the second
The vaporized gas enters the container 5, where it is valved, and passes through the valves 24 and 20. By continuing to repeat the above operations, the undoped GmA+s active layer 34, p-type Gm, -xAZ, cAs cladding layer 35, and p-type G
The aAs cap layer 36 is grown in sequence to produce a five-layer double heterostructure compound semiconductor substrate.

Note that the conductivity type of each growth layer above is 10 in the case of n-type.
It is highly controlled by flowing ppm H2Se gas/H2 gas 8 and DEZ in the third container 6 in the case of p-type according to respective predetermined doping amounts.

By the way, in the prior art, each growth layer of a compound semiconductor substrate is formed while maintaining a constant growth rate without changing the overall flow rate of gas and the flow rate of hydride gas such as AsH3 gas.

However, in this method, the interface between each growth layer, specifically the n-type GaAs/Gtuff layer 31 and the n-type Ga
1-Air AtXAs cladding layer 32 interface and p-type G
a 1□htx" The discontinuity between the cladding layer 34 and the p-type GaAa cap layer 35 outside the layer 5 is not good, and an interface with good steepness cannot be obtained. This has the disadvantage that light confinement at the interface becomes insufficient during device fabrication.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a compound semiconductor substrate that can obtain an interface with good steepness between growth layers of different compositions on a compound semiconductor substrate.

[Summary of the invention]

The present invention is characterized in that the overall gas flow rate flowing into the reactor near the interface between growth layers of different compositions remains constant, and the flow rate of the organometallic gas is changed to control the growth rate of the growth layer. As a result, a well-steep interface can be obtained between the grown layers having different compositions, thereby improving device characteristics.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

The growth apparatus used in forming the growth layer is the one shown in FIG. 2 described above, and the same members are given the same reference numerals and the explanation thereof will be omitted.

The feature of the present invention is that the overall gas flow rate is constant and %
nm GaAs buffer layer 32 and n-type Ga, -xA
Near the interface of the txAII cladding layer 33, near the interface between this cladding layer 33 and the AND-1GmAg active layer 34, near the interface between this active layer 34 and the p-type Ga 1-XAZXAZ layer 35, and near the interface between this cladding layer 35 and the p-type Ga
Organometallic gas and As
By decreasing the flow rate of Hs gas, the epitaxial growth rate was increased from 0.3 to 0.05μ: m7'm1 as shown in Figure 1.
The point is to reduce it to n.

At this time, the flow rate of H2 gas as a carrier gas is adjusted in response to the change in the flow rate of the organometallic gas or AsHs gas, so that the overall gas flow rate flowing through the bell jar I is kept constant.

Next, a specific example of manufacturing a compound semiconductor substrate by the method of the present invention will be described. First, an n-type GaAs+ substrate 31 is placed on the susceptor 2, and the susceptor 2 is heated to 700 to 800° C. by the high frequency coil 3. At that time, inside the belljar 1, there is a 1
About 10% of H2 gas and carrier gas of 0% A@H are flowed. When the susceptor temperature reaches the set value, the flow rate of AsH3 is changed to TMG -? TMA
The molar ratio of TMG to TMG is about 10 to 30.
is bubbled with H2 gas, the vaporized gas is drawn into the bell jar 1, and the growth of the n-type GaAs buffer layer 32 is started. In addition, H2 gas 9 is Con) o-514, pulp 2
3 and enters the first container 4, the vaporized gas is pulp 22,
Pass through pulp 2o. Here, the epitaxial growth rate is determined by the flow rate of TMG, and is approximately 0.3μVm1
Let it be n. The thickness of the buffer layer 32 is about 1 .mu.m, but when it has grown to 0.5 to 0.9 .mu.m, the nozzle 22 is closed and the cap 21 is opened to temporarily stop the growth of the buffer layer 32. Then, the flow rate of TMG was reduced and the growth rate was reduced to 0.0.
At 5 μm1rth in, gas is again introduced into the bell jar 1 to start growth. When the buffer layer 32 grows to a thickness of 1 μm, the gas is switched again to stop the growth.

Next, an n-type Ga, -XAtXAs cladding layer 33
growth. Here, the AtA3 mixed crystal ratio X is about 0.1 to 0.5 as shown by the solid line in FIG. And T
TMA gas is flowed at the same time as MG, and its composition is 0.1~
Growth is started by adjusting the flow rate so that the flow rate is 0.5 and the growth rate is 0.05 μm/ml n as in the case of the buffer layer 32.

When the cladding layer 33 has grown to 0.5 to 0.9 μm, the gas is switched and the growth rate is returned to 0.3 μ$in.

Thereafter, the operation of decreasing the growth rate in layers near the interface with different compositions and increasing the growth rate in other bulk regions may be repeated. However, undoped GaA
s In the active layer 34 region, the thickness of the growth layer is generally 50.1μ.
Since the film is very thin (m), the growth rate is set to a low value.

Therefore, according to the present invention, near the interface between growth layers having different compositions, that is, the n-type GaAs buffer layer 32 and the n-type G
a 1□ Near the interface of AtxAs cladding layer 33, p-type Ga, -XAtXAs cladding layer 35 and p-type GaA
While the overall gas flow rate remained constant near the interface of the s-cap layer 36, the flow rates of the organometallic gas and the As H5 gas were decreased to reduce the epitaxial growth rate to 0.05 μVmi.
Since the growth rate is controlled by reducing the growth rate to n, it is possible to obtain an interface with good steepness between each growth layer. Therefore, when a semiconductor radar or a light emitting diode is manufactured from the compound semiconductor substrate obtained in this manner, the element loading effect is improved and an element with good characteristics can be obtained. For reference, the At mixed crystal ratio in the conventional case is as shown by the dashed line in FIG.

In the above embodiment, the mass flow controller and the air-operated pulp are operated manually, but this is not limited to this. For example, when these are operated automatically by 'i CUP control, etc., the mass flow controller and the air operated pulp are operated manually as shown in FIG. TMG −? near the interface between different growth layers like this? The growth rate may be changed by gradually changing the mass flow rate of TMA.

Further, in the above embodiment, GaA is used as the compound semiconductor substrate.
Although the case has been described in which an s-substrate (III-V group) is used, the present invention is not limited to this, and an n-M group compound semiconductor substrate may also be used.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a method for manufacturing a compound semiconductor substrate that can obtain a steep interface between growth layers having different compositions, thereby improving device characteristics.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the bi-taxial growth rate of each growth layer of a GaAs substrate according to an embodiment of the present invention, and FIG. 2 is a growth apparatus used in the conventional and present invention for manufacturing compound semiconductor substrates. 3 is a cross-sectional view of the GaAs substrate, FIG. 4 is a characteristic diagram showing the AtAa mixed crystal ratio of each growth layer of the GaAs substrate according to the method of the present invention, and FIG. 5 is another example of the present invention. FIG. 3 is a characteristic diagram showing the epitaxial growth rate of each growth layer of the GaAs substrate according to the invention. 1... Bell jar, 2... Susceptor, 3... High frequency coil, 4, 5. , 6... Container, 7... AsH
3/H3 gas, 8...H2S@gas/H2 gas, 9.
...H2 gas, 10-16...mass 70--control 5.17-27...air operation valve, 31...n
type GaAs substrate, 32... n-type GaAs buffer layer, 33... n-type Ga, -xAJLxAs cladding layer, 34-... undoped GmAm active layer, 35...
・PM Ga 1-xAtxAa layer, 36
...p-type GaA1 layer. Applicant's representative Patent attorney Takehiko Suzue Figure 3 Figure 4 Figure 5 Commissioner of the Patent Office Manabu Shiga 1. Display of the case Japanese Patent Application No. 139985/1985 2, Name of the invention Method for manufacturing compound semiconductor substrate 3, Person making the amendment Relationship to the case Patent applicant (307) Norishi Co., Ltd. 4, Agent 7, Contents of the amendment As not included in the attached sheet, the figure number "Figure 2" is on the first page of the drawing.
join.

Claims (2)

[Claims] (1) In a method for manufacturing a compound semiconductor substrate in which a plurality of growth layers are grown on a III-V or II-VI compound semiconductor substrate by organometallic pyrolysis, a reactor is placed near the interface between the growth layers with different compositions. A method for manufacturing a compound semiconductor substrate, characterized in that the growth rate of a growth layer is controlled by changing the flow rate of an organometallic gas while keeping the overall gas flow rate constant. (2) The method for manufacturing a compound semiconductor substrate according to claim 1, characterized in that the flow rate of another gas serving as a raw material for the growth layer is also changed together with the organometallic gas.