JPH0425120A - Manufacture of compound semiconductor layer - Google Patents

Abstract

PURPOSE:To make it possible to obtain a compound semiconductor device provided with an AlXGa1-XAs crystal layer having excellent crystallinity by a method wherein a substrate is heated up to the temperature at which the In of a crystal layer is evaporated while an As molecular beams is being projected on the surface of an (AlYGa1-Y)0.5P crystal layer (0<=Y<=1) which is latice- matched with a GaAs substrate. CONSTITUTION:An (AlYGa1-Y)0.5infinity n0.5P crystal layer (0<=Y<=1), with which a lattice matching is performed, is formed on a GaAs substrate 11, the substrate 1 is heated up to the temperature at which the In of the crystal layer 14 will be evaporated by projecting an As molecular beam on the surface of the crystal layer 14, and the surface of the crystal layer 14 is converted to several molecular layers of AlYGa1-YAs crystal layer 15 (0<=Y<=1). Then, an AlXGa1-XAs crystal layer 16 (0<=X<=1) is formed on the AlYGa1-YAs crystal layer 15. As a result, an AlXGa1-XAs crystal layer 16 of high quality, which is lattice matched to the substrate 1, can be formed easily without deterioration on the surface of the (AlYGa1-Y)0.5In0.5P crystal layer 14.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing a compound semiconductor layer, and in particular, to a method for manufacturing a compound semiconductor layer.
The present invention relates to a method for manufacturing a compound semiconductor layer that can form a compound semiconductor layer belonging to Group V on a GaAs substrate with good crystallinity.

(Prior Art) In recent years, in order to improve the functionality of optical information processing systems, there has been a demand for the realization of semiconductor laser elements that oscillate in a shorter wavelength range.

Lattice matched to GaAs substrate (A I yG a +-
v) e,s In 11. SP crystal (0≦Y≦1) is
It is attracting attention as a material for visible light semiconductor lasers that emit light with a wavelength in the 600 nm band. Hereinafter, in this specification, unless otherwise specified, (AIYGa
I-Y) 11.5r n lI, 5P (0≦Y≦1
) is referred to as AlGa1nP or GaInP (in the case of Y=O).

In addition to metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) is a promising method for growing AIGaInP crystals on a substrate.

There is a report that an AlGa InP visible light semiconductor laser device fabricated using the MBE method continuously oscillated visible light at room temperature (Hayakawa, et al., J.
Our own of Cry=2 5tal Growth 95 (198
9)pp, 949).

Figure 5 shows the conventional AIGa created by the 'MBE method.
1 shows a cross-sectional view of an InP-based visible light semiconductor laser device.

A first conductivity type GaAs/'y layer 2, a first conductivity type Ga I nP buffer layer 3, and a first conductivity type AlGa InP are grown on a first conductivity type GaAs substrate 1 by the MBE method. A cladding layer 4, a GaInP active layer 5, a second conductivity type AIGaInP second cladding layer 6, and a second conductivity type GaInP layer 20 are laminated in this order from the substrate 1 side.

An insulating silicon nitride film 21 is formed on the second conductivity type GaInP layer 20, and the silicon nitride film 21 includes:
Striped grooves with a width of 10 μm reaching the second conductivity type Ga I nPP2O3 are formed.

An electrode 23 is provided on the upper surface of the above laminated structure and the back surface of the substrate 1.
．． 22 is formed.

The semiconductor laser device shown in FIG. 5 is a gain waveguide semiconductor laser device in which an insulating silicon nitride film 21 having striped grooves narrows the current.

This semiconductor laser device exhibits an oscillation threshold of 93 mA and is also capable of continuously oscillating visible light at room temperature.

(Problems to be Solved by the Invention) However, the above-mentioned conventional technology has the following problems.

The semiconductor laser device shown in Figure 5 has a maximum continuous oscillation temperature of 35°C due to poor dissipation of heat generated in the active layer during oscillation.
It was low. This is because the thermal conductivity of AIGaInP crystal is low.

In order to manufacture a semiconductor laser device that has a structure with excellent heat dissipation and a double heterostructure made of AIGaInP crystal lattice matched to a GaAs substrate, it is necessary to use Al
It is sufficient if an AlGaAs crystal layer, which is a material with relatively high thermal conductivity and excellent heat dissipation properties, can be formed on the Ga1nP crystal layer by the MBE method.

However, when forming an AlGaAs crystal layer on an AIGaInP crystal layer that is lattice-matched to the GaAs substrate by the MB=4=E method, if the surface of the AIGaInP crystal layer is contaminated with impurities, the surface of the AlGaInP crystal layer may be contaminated with impurities. However, there is a problem in that an AlGaAs crystal layer with excellent crystallinity cannot be grown.

Such contamination can cause damage to the AI Ga InP crystal layer and the Al
When the GaAs crystal layer is formed continuously by the MBE method, after the growth of the AIGaInP crystal layer is completed, the P
This also occurs when layer growth is temporarily stopped in order to switch from molecular beam irradiation to As molecular beam irradiation.

This is because impurities such as oxygen and water vapor in the atmosphere inside the MBE apparatus are removed within a few seconds after the above-mentioned temporary crystal layer growth stops.
This is because it contaminates the surface of the crystal layer where growth has stopped.

Furthermore, when growing a high quality AlGaAs layer by the MBE method, it is necessary to raise the substrate temperature to about 620°C. At this temperature, however, intensive evaporation of In or P from the AlGaInP layer causes the AIGa
There is a problem in that the surface of the InP crystal layer deteriorates. On the AIGaInP crystal layer with such surface deterioration, AlGaAslG
If the aAs crystal old layer is used, an AlGaAs crystal layer with excellent crystallinity cannot be obtained.

The present invention has been made to solve the above problems, and its purpose is to lattice match (A 1 yG a 1-Y) LSI ne, s to a GaAs substrate.
Even when the surface of the P crystal layer is contaminated, its (AI Y
To provide a method for manufacturing a compound semiconductor layer that can easily form a high quality A I It is in.

Another object of the present invention is to lattice match the GaAs substrate (
A I YG a +-y) e, s I n II,
Without deteriorating the surface of the sP crystal layer, its (AI
An object of the present invention is to provide a method for manufacturing a compound semiconductor layer that can easily form a high quality A I XG a 1-XAs crystal layer on a YG a ty) e51rz+, sP crystal layer.

(Means for Solving the Problems) The method for manufacturing a compound semiconductor layer of the present invention provides (AlyGa+-y)s, 51n, which is lattice matched to a GaA-S substrate.
A step of forming an e5P crystal layer (O≦Y≦1) on the substrate, and raising the substrate to a temperature at which In in the crystal layer evaporates while irradiating the surface of the crystal layer with an As molecular beam. By heating the surface of the crystal layer, several molecular layers of A I yG a
1-yA s crystal layer (0≦Y≦1), and A I
) on the A 1 yG a 1-vAs crystal layer, thereby achieving the above object.

(Example) The present invention will be described below with reference to Examples.

First, a first embodiment will be described with reference to FIG.

As shown in FIG. 1(a), first, a GaAs buffer layer 12 and an (AI 11.7G
a i+, a) s, s I n T! , 6P layer 14
were grown in this order from the substrate 11 side by the MBE method. The substrate temperature at this time was 510°C.

Next, after stopping the bimolecular beam irradiation, (AIθ7G
a [1,3) e, s I n [! , while irradiating the 5P layer 14 with the As molecular beam, the substrate temperature was increased to 620°C.
A process was performed in which the temperature was raised to 'C' and this state was maintained for several minutes.

Through this process, (A 1 n, 7G a 11.
3) I near the surface of the 11.5 I n8.5P layer 14
By replacing n and P with As in the As molecular beam,
(A I [1, TG a 8, s) [1,5I n
+! , several molecular layers near the layer surface 4 of the sP layer 14 are several molecular layers A l l! , 7G a [1,3A 3-layer 15].

A l l of this few molecular layers! , 7G a 11. aA
The third layer 15 is a layer made of a thermally stable material whose constituent elements hardly evaporate at temperatures below about 680°C.

For this reason, the (
A I 11.7G a s, 3) s, s I n
e, evaporation of In or P from the sP layer 14 was prevented by being covered with several molecular layers of the Al t+,yG a [1,3As layer 15.

In this way, by performing the above steps, especially 580
It becomes noticeable at temperatures above about °C (Ali!).

7G a [1,3) [! , 5 I n s, deterioration due to evaporation of In or P in the sP layer 14 is suppressed at about 620°C 1
There are seven things that can be done to prevent this from happening.

After the above-mentioned process of raising the substrate temperature to 620°C while irradiating the As molecular beam, in succession to that process, Al 11,4G a 9. aA AI 3 layer 16
i! .

A step of growing on the 7Gaa3As layer 15 was performed.

The growth of this A 1 g, 4G a e, eA three layer 16 was performed by a normal MBE method in which the substrate 11 is irradiated with an A1 molecular beam and a Ga molecular beam in addition to the As molecular beam.

The substrate temperature at this time was 620°C. AIθ, 4G a formed by the method of the first example 8. aA
The substrate temperature is increased to 62°C while irradiating the S layer 16 and the As molecular beam.
In order to compare each A
Photoluminescence of the Gaθ, BA s layer was measured.

As a result, the emission intensity of the example was several times higher than that of the comparative example. This is true for AI 9,4 in Example
G a 9. aA The crystallinity of the three layers 16 is that of Comparative Example A
I [1,4G a 6. This shows that the crystallinity is superior to that of the BAs layer.

The first reason why the A I 11.4G a g, 6A s layer 16 having such excellent crystallinity could be formed by the method of the above-described embodiment is that A l e, aG a e,
By performing the above-mentioned process of increasing the substrate temperature to 620°C while irradiating As molecular beams before growing the 6A s layer 16, (A I e, rG a [1,3)
[! , 5 Ine, several molecular layers near the surface of the sP layer 14 are changed to several molecular layers of the AlGaAs layer 15, and by this layer, (A1[1,7G a 11.3) 11
．． This is because deterioration of the s I n 11.5P layer 14 due to evaporation of In and P was prevented.

The second reason is A I i! ,4G a[1,eA
Before the growth of the s-layer 16, during the above-mentioned step of increasing the substrate temperature to 620°C while irradiating the As molecular beam, (
A1 e, 7G a 11.3) [1,5I n e
, By replacing In and P near the surface of the sP layer 14 with As in the As molecular beam, (A 1 a, yG a
e, 3) [! This is because impurities such as oxides existing near the surface of the , 5 r n B, 5P layer 14 were removed, thereby cleaning the surface area.

In this way, in this example, even if the MB is
Even if the surface of the crystal layer where growth has stopped is contaminated by impurities such as oxygen and water vapor in the atmosphere inside the E equipment, the contamination will be cleaned by the method described above, so problems caused by switching the molecular beam irradiation will not occur. There wasn't.

Next, a second embodiment will be described with reference to FIG.

As shown in FIG. 2(a), first, a GaAs buffer layer 12 and a GaInP layer 13 were grown in this order on a GaAs substrate 11 from the substrate 11 side by the MBE method. The substrate temperature at this time was in the range of 450 to 570°C.

Thereafter, the substrate 11 was taken out of the MBE apparatus for surface observation. Thereafter, the substrate 11 was introduced into the MBE apparatus again, and the GaInP layer 13 was irradiated with an As molecular beam, the substrate temperature was raised to 620°C, and this state was maintained for several minutes. .

By this step, In near the surface of the GalnP layer 13
By substituting As and P for As in the As molecular beam, G
Several molecular layers near the surface of the alnP layer 13 are several molecular layers of G.
It changed to an aAs layer 17.

This several molecular layer GaAs layer 17 is a layer made of a thermally stable material in which almost no evaporation of the constituent elements occurs at temperatures below about 680°C. For this reason, In or P from the GalnP layer 13, which would normally occur actively at about 620°C,
This evaporation was prevented by covering the GaAs layer 17 with several molecular layers.

In this way, by performing the above steps, especially 580
The I of the GalnP layer 13 becomes noticeable at temperatures above about °C.
Deterioration due to evaporation of n or P could be prevented even at about 620°C.

After the above-mentioned step of raising the substrate temperature to 620°C while irradiating the As molecular beam, following that step,
A l 11.7G a 11.3A 6 layers 18 are Ga
A step of increasing the AS layer 17 between the layers 7 was performed. This A1[!
, 7G a l! , 3As The growth of the s layer 18 was performed by the usual MBE method in which the substrate 11 is irradiated with an A1 molecular beam and a Ga molecular beam in addition to the As molecular beam. The substrate temperature at this time was 690°C.

The AlGaAs layer 18 thus formed also has the same characteristics as the AlGaAs layer 16 formed by the method of the first embodiment.
It had excellent crystallinity.

Next, a third embodiment will be described with reference to FIG.

First, a first conductivity type GaAs substrate 1 is coated with a first conductivity type GaAs substrate 1.
As buffer layer 2, first conductivity type GaInP buffer layer 3
, first conductivity type AIGaInP cladding layer 4, Ga I
An nP active layer 5, a second conductivity type AIGaInP second cladding layer 6, and a second conductivity type GaInP layer 7 were grown in this order from the substrate 1 side by the MBE method (Fig. 3(a)).
). The growth of these layers is performed using MB, which treats P as a molecular beam source.
This was carried out using the usual MBE method in an E apparatus. Note that the substrate temperature at that time was 510°C. Further, the layer thickness of the second conductivity type GaInP layer 7 was set to 100A.

Thereafter, the substrate 1 was taken out of the MBE apparatus and then introduced into another MBE apparatus that uses As as a molecular beam source.

Next, in this MBE apparatus, the second conductivity type Ga1nP layer 7
Above 1: While irradiating the As molecular beam, increase the substrate temperature to 620°.
A step was performed in which the temperature was raised to C and this state was maintained for several minutes.

Through this process, In and P near the surface of the GalnP layer 7 are replaced with As in the As molecular beam, so that Ga
Several molecular layers near the surface of the I nP layer 70 are several molecular layers of G
a A's layer 8 (FIG. 3(b)).

After growing a second conductivity type GaAs cap layer 9 on the GaAs layer 8 by the MBE method, an insulating silicon nitride film 21 is grown on the second conductivity type GaAs cap layer 9 by plasma C.
It was grown by the VD method.

By photo-etching the silicon nitride film 21, a width of 10 μm is formed to reach the second conductivity type GaAs cap layer 9.
Striped grooves were formed in the silicon nitride film 21.

By forming electrodes 23 and 22 on the top surface of the laminated structure thus formed and on the back surface of the substrate 1, as shown in FIG.
A gain waveguide type semiconductor laser device shown in C) was fabricated.

This semiconductor laser device continuously oscillated light with a wavelength of 670 nm at room temperature.

Since this semiconductor laser device has a second conductivity type GaAs cap layer 9 made of GaAs, which has better thermal conductivity than GaInP, the heat generated in the active layer 5 is efficiently dissipated to the outside of the semiconductor laser device. be done. Therefore, it was possible to achieve temperature characteristics superior to those of the semiconductor laser device shown in FIG.

In the semiconductor laser device (comparative example) fabricated using the above fabrication method that omitted the step of raising the substrate temperature to 620°C while irradiating the As molecular beam, the oscillation threshold increased, so continuous operation at room temperature was It was not possible to realize oscillation. This is because after the surface of the second conductivity type Ga1nP layer 7 of this semiconductor laser device was contaminated by contact with the atmosphere, a crystal layer was grown on it without being sufficiently cleaned in the MBE apparatus. . For this reason, the crystallinity of the crystal layer formed above the second conductivity type GaInP layer of the comparative example was inferior to that of the example;
The luminous efficiency of the laser beam of the comparative example decreased.

Next, a fourth embodiment will be described with reference to FIG.

First, a first conductivity type GaAs substrate l is coated with a first conductivity type GaAs substrate l.
The 1nP buffer layer 3, the GaInP active layer 5, and the second conductivity type GaInP layer 6 are formed in this order from the substrate side by
It was grown by the BE method. The growth of these layers was performed by the usual MBE method in an MBE apparatus using P as a molecular beam source.

Thereafter, the substrate 1 was taken out of the MBE apparatus and then introduced into another MBE apparatus that uses As as a molecular beam source.

Next, in this MBE device, the second conductivity type Ga1nP layer 6
While irradiating the top with As molecular beam, the substrate temperature was increased to 620°C.
The process involved raising the temperature to a certain temperature and maintaining that state for several minutes.

Through this process, In and P near the surface of the GaInP layer 6 are replaced with As in the As molecular beam, so that Ga
The low tide of several minutes near the InPPO2 surface changed to the GaAs layer 8 of several minutes of low tide.

After growing a second conductivity type GaAs layer 9 on the GaAs layer 8, electrodes 23 and 22 were formed on the second conductivity type GaA's layer 9 and the back surface of the substrate 1.

Thereafter, the electrode 23 and a predetermined region of the second conductive type GaAs layer 9 were etched to the surface of the second conductive type GaInP layer 6, thereby forming a light receiving part of the photodiode.

Next, the electrode 23, the second conductivity type GaAs layer 9, the GaAs layer 8, the GaInP layer 6, the GaInP active layer 5 and the first
By etching a predetermined portion of the conductive GaInP buffer layer 3, a pIn type photodiode shown in FIG. 4 was fabricated.

In the MBE apparatus, the second conductivity type Ga I nP layer 6 described above is
While irradiating the top with As molecular beam, the substrate temperature was increased to 620°C.
The sensitivity of the PLN photodiode of this example was superior to the sensitivity of the PIN photodiode manufactured without performing the step of increasing the sensitivity. This is M
This is because even at the interface of the grown layer where layer growth by the BE method was temporarily stopped, the formation of an interface layer was reduced by the method of this embodiment.

In this way, even if the surface of the AIGaInP crystal layer, which is lattice-matched to the GaAs substrate, becomes contaminated during the manufacturing process,
Since a high-quality AlGaAs crystal layer can be easily formed thereon, not only high-quality semiconductor laser elements but also various compound semiconductor devices such as photodiodes can be provided.

(Effects of the Invention) As described above, in the present invention, the GaAs substrate is lattice-matched (
A 1 yG a I-Y) [1,51ne;s
While irradiating the surface of the P crystal layer (0≦Y≦1) with an As molecular beam, the substrate is heated to a temperature at which In in the crystal layer evaporates, and the surface of the crystal layer is heated at low tide for several minutes. AlvG
It can be changed to a + -yA S crystal layer (0≦Y≦1). For this reason, (A lyG a I-Y
) [The surface of the 1,51n11.5P crystal layer)n was purified, and (Al-18=yG a +-y) a,s I n 1! , evaporation of In and P from 5P can be prevented.

In addition, the A I yG a I-YA S of several molecular layers
On the crystal layer, an A I XG a 1-XA S crystal layer (
O≦X≦1), the A 1 yG a +−
yA Because the surface of the S crystal layer is cleaned, the A
The crystallinity of the IXG a I-XA S crystal layer is of high quality.

Therefore, according to the method for manufacturing a compound semiconductor layer of the present invention,
(A 1 yG a I-Y) 11.5 I n
8. A I XG with excellent crystallinity on the sP crystal layer
A high quality compound semiconductor device including an a + -xA s crystal layer can be provided.

4. of. Nagoya I Fig. 1 is a sectional view showing the first embodiment of the present invention, Fig. 2 is a sectional view showing the second embodiment, Fig. 3 is a sectional view showing the third embodiment, and Fig. 4 is a sectional view showing the third embodiment. The figure is a sectional view showing the fourth embodiment, and FIG. 5 is a sectional view showing a conventional example.

I... GaAs substrate of first conductivity type, 2... GaAs buffer layer of first conductivity type, 3... GaInP buffer layer of first conductivity type, 4... AIGaInP first cladding layer of first conductivity type, 5 ...GaInP active layer, 6... second conductivity type AlGa'InP second cladding layer, 7... second conductivity type GaInP layer, 8-GaAs layer, 9...
・Second conductivity type GaAs cap layer, 11...GaAs
Substrate, 12--GaAs buffer layer, 13--
GalnP layer, 14-=AI Ga I nP layer, 15
...AlGaAs layer, 16-= AI Ga A
s layer, 17---GaAs layer, 18---AlGaA
s layer, 20... Second conductivity type GaInP layer, 21...
・Silicon nitride 22.23...electrode.

that's all

Claims (1)

[Claims] 1. Lattice matching to GaAs substrate (Al_YGa_1_
-_Y)_0_. _5In_0_. _5P crystal layer (0≦
Y≦1) on the substrate, and heating the substrate to a temperature at which In in the crystal layer evaporates while irradiating the surface of the crystal layer with an As molecular beam.
The surface of the crystal layer is coated with several molecular layers of Al_YGa_1_-_Y
Manufacture of a compound semiconductor layer including a step of changing into an As crystal layer (0≦Y≦1), and a step of forming an Al_XGa_1_-_XAs crystal layer (0≦X≦1) on the Al_YGa_1_-_YAs crystal layer. Method.