JPH0658976B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for manufacturing a compound semiconductor device, and more specifically,
The present invention relates to a method for manufacturing an aluminum gallium arsenide-based compound semiconductor device having a pn junction formed by adding a single impurity, which is useful for a light emitting element, a transistor, and the like.

[Conventional technology]

Liquid phase epitaxy of compound semiconductors includes, for example, molten gallium (Ga)
Gallium arsenide (GaAs), aluminum (Al) and appropriate impurities are dissolved in the solution at high temperature to make a saturated solution of aluminum gallium arsenide (AlGaAs), and this saturated Ga solution is brought into contact with the GaAs or AlGaAs substrate and gradually cooled. By AlGaAs
It consists of growing crystals.

In order to obtain a compound semiconductor having a pn junction by this liquid phase growth method, generally, p-type impurities and p-type impurities exhibiting p-type conductivity are used.
There is a method of forming from a solution added with an n-type impurity exhibiting type conductivity or a solution added with an amphoteric impurity exhibiting both p-type and n-type conductivity.

Conventionally, due to crystal growth in GaAs and Al _x Ga _1-x As
When forming a pn junction, Zn, Be, M are generally used as p-type impurities.
Although g is used, these impurities move by diffusion during crystal growth and subsequent heat treatment, so the initial position of the pn junction moves to the n-type side. Is difficult to control. This will be explained with reference to FIG. 5 for a conventional AlGaAs pn junction. The n-type GaAs is formed by liquid phase epitaxial growth.
N-type Al _x Ga _1-x As layer doped with n-type impurity Te on the substrate 11
12 was crystal-grown and then p-doped with p-type impurity Zn
An Al _y Ga _1-y As layer 14 is epitaxially grown on the n-type layer 12. In this case, the position 16 of the pn junction should be at the interface between the n-type layer 12 and the p-type layer 14 unless the impurity Zn originally diffuses. However, during the crystal growth of the p-type Al _y Ga _1-y As layer 14, movement due to diffusion of the impurity Zn occurs and pn
The bonding surface moves from the initial bonding position 16 into the n-type Al _x Ga _1-x As layer 12. The moved joining position 15 is indicated by a broken line. Therefore, the p-type Al _x Ga _1-x As layer 13 is formed in the n-type layer as shown in the figure. The phenomenon in which the pn junction surface is displaced is such that x ≠
problem when y heterojunction, going to made a hetero p-n junction is actually, p-type Al _x Ga _1-x As layer 13 and the n-type Al _x Ga _1-x As
Since it becomes a homo pn junction with the layer 12, the effect of confining carriers when used as a light emitting element, the efficiency of injecting a small number of carriers, etc. decreases, and the light emitting efficiency deteriorates. When doped p-type AlGaAs is used as a base, Zn diffuses toward the n-type emitter and collector sides to widen the width of the base, which causes a problem of deterioration in frequency characteristics.

On the other hand, it is shown in GaAs that silicon (Si), which is a Group IV element, is an amphoteric impurity exhibiting p-type and n-type conductivity, and ambipolarity is also expected for germanium (Ge), which is a homologous group. ing. Especially, Si is GaAs by adding the same impurities.
It is possible to form a pn junction therein, and the pn junction position does not fluctuate as seen in the pn junction formed by the above different impurities during the crystal growth process and the subsequent heat treatment. Has been put into practical use.

As described above, if a pn junction can be formed by adding the same impurities, good characteristics can be obtained without movement of the pn junction. Therefore, even in the Al _x Ga _1-x As (0 <x <1) system, , Which is required for photo detectors and transistors, but in liquid phase epitaxy, AlGaAs containing Al contains impurities such as Si.
In, the p-type conductivity at the practical carrier concentration is not obtained. With the impurity Ge, n-type conductivity was not obtained. It is considered that the reason for this is that the growth conditions are narrow and limited and that it was not carefully examined.

[Problems to be solved by the invention]

Impurity Ge is Al _x G in the conventional liquid phase epitaxial growth method.
a _1-x As (0 <x <1) shows only p-type conductivity, and molecular beam epitaxial growth shows only n-type conductivity. Therefore, the same growth method shows n-type and p-type conductivity. It was said that they could not be controlled at the same time.

On the other hand, even if the above-mentioned two types of growth methods are used, it is difficult to control the pn junction interface, and thus a pn junction has not yet been obtained.

However, if an Al _x Ga _1-x As (0 <x <1) system having a pn junction is formed by the same impurity Ge, as described above, p
It is expected that a good compound semiconductor device with almost no diffusion can be obtained because the impurity concentration at the pn junction interface decreases and the diffusion coefficient of Ge does not change.

Therefore, in the present invention, the same impurity Ge is used.
Al _x Ga _1-x As (0 <x <1) and p-type Al _y Ga _1-y
It is intended to provide a method for producing a compound semiconductor having a pn junction with As (0 <y <1).

[Means for solving problems]

The present inventors have paid attention to the Ge impurity that has been conventionally used to form p-type AlGaAs, and conducted a detailed doping experiment on the impurity. As a result, even in the conventional AlGaAs liquid phase growth method, the crystal growth temperature was increased. , and a constant amount of Ge to Ga solution and gradually increasing the amount or x value of the growing AlGa _1-x As of Al, growing Al _x Ga _1-x As is certain x
It was found that the p-type changes to the n-type when the value exceeds the value.

Therefore, the manufacturing method of the compound semiconductor device of the present invention is
Substrate and Al _x Ga _1-x A having n-type conductivity formed by adding germanium (Ge) as an impurity formed on the substrate
s (0 <x <1) layer and Al _y Ga exhibiting p-type conductivity
_1-y As (0 <y <1) layer (where x and y are 0 <y
<X <1) and at least one pn junction, wherein both layers contain germanium as an impurity and contain aluminum (Al) and arsenic (As). Is formed by liquid phase epitaxial growth on a substrate by bringing the Al _y Ga _1-y As layer into contact with a gallium (Ga) solution, and the Al _y Ga _1-y As layer has a predetermined germanium concentration. In the liquid phase epitaxial growth characteristic curve in which the crystal layer to be formed changes from the p-type to the n-type with the minimum value of the carrier concentration as the boundary when the amount of aluminum is increased, The Al _x Ga _1-x As layer formed by contacting with a gallium solution containing a predetermined amount of aluminum is in front of the side where the n-type is formed. It is characterized in that it is formed by contacting with a gallium solution containing an amount of aluminum larger than the predetermined amount of aluminum.

In the method of manufacturing a compound semiconductor device of the present invention, GaA
On the s substrate, the first Al _x Ga _1-x As (0 <x
<1) The second Al _y G in which the layer is formed and germanium having a conductivity different from that of the first layer is added as an impurity
It is preferable that an a _1-y As (0 <y <1) layer is formed on the first layer, and an electrode is formed on the GaAs substrate and the Al _y Ga _1-y As layer. , A diode can be manufactured.

Further, in the method for manufacturing a compound semiconductor device of the present invention,
On the GaAs substrate, the first Al _x Ga _1-x As doped with germanium having the same conductivity as the substrate as an impurity.
And a second Al _y Ga _1-y As (0 <y <1) layer doped with germanium having a conductivity different from that of the first layer is formed. A third Al _z Ga _{1 -z} As (0) layer formed on the first layer and doped with germanium having the same conductivity as the first layer is added.
A <z <1) layer (where y and z have a relationship of 0 <y <z <1) is formed on the second layer, and
As substrate, Al _y Ga _1-y As layer and Al _z Ga _1-z As
A method in which an electrode is formed on a layer is also preferable, and a transistor can be manufactured by this method, for example.

Hereinafter, the present invention will be described more specifically.

In the conventional liquid phase epitaxial growth method, p-type Al _x Ga _1-x As
At that time, about 0.01 g of Ge per Galg was added to a Ga solution (melt solution) containing a predetermined amount of GaAs and Al. The present inventors have made various changes in the Al composition of Al _x Ga _1-x As on a GaAs substrate under the condition that the added amount of Ge is smaller than that of the conventional one, for example, 0.005 g per Galg or 0.002 g. Let me
When liquid phase growth was performed at a saturation temperature of 800 ° C., as shown in FIG. 1, when the Al composition value x was increased even when the Ge addition amount was the same, that is, when the Al addition amount to the Ge solution was increased. ,
It has been found that crystal-growing Al _x Ga _1-x As changes from a conventionally known p-type to an n-type that has not been known until now. To be more specific, first, GaAs having a weight capable of growing Al _0.3 Ga _0.7 As and 0.002 g of Ge per Al and Galg are added in Ga at 800 ° C.
Then, the Ga solution is melted, and the Ga solution is brought into contact with the p-type GaAs substrate 1 as shown in FIG. Al _0.3 Ga _0.7 As
Layer 2 (carrier concentration = 10 ¹⁷ cm ⁻³ ) grows. Continued
Al _0.65 Ga _0.35 As grows so much GaAs and Al and
When 0.002 g of Ge per Galg was dissolved in Ga at 800 ° C., a Ga solution was brought into contact with the first layer 2 and slowly cooled. When the Ga solution was removed, n-type Al _0.65 Ga was formed on the first layer 2. _0.35 As layer 3 (carrier concentration = 10 ¹⁷ cm ⁻³ ) grows and n-type Al _0.65 Ga _0.35 As−
A hetero pn junction of p-type Al _0.3 Ga _0.7 As can be formed. When the cross-section of the hetero pn junction produced by the method of the present invention is observed by SEM, the peak 5 of the electromotive force signal induced by the electron beam indicating the position of the pn junction is obtained.
Indicates that the heterojunction interface 6 and the pn junction do not separate during crystal growth as described with reference to FIG. 5 (see FIG. 2).

The value of x in the above pn inversion decreases due to the decrease in the added amount of the impurity Ge. As shown in FIG. 1, the added amount of Ge is 0.00
The molar fraction of AlAs at 2 g is smaller than that at 0.005 g. It was also found that the value of x in pn inversion decreases with the increase of the saturation temperature when the amount of Ge added in the Ga solution is constant.

As described above, from the growth characteristics of Al _x Ga _1-x As added with Ge as an impurity in the liquid phase growth method, the amount of Ge added and the amount of Al added in the Ga solution, and the saturation temperature of the Ga solution (almost By selecting the conditions (equal to the growth temperature), the same impurity
Ge can be added to grow n-type and p-type Al _x Ga _1-x As. As can be seen from the results of FIG. 1, a homo-pn junction of Al _x Ga _1-x As is possible by changing the amount of Ge added between the n-type layer and the p-type layer.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 An example of a diode manufactured by the method of the present invention will be described with reference to FIG.

As shown in FIG. 3, as impurities on the n-type GaAs substrate 31
Ge-added n-type Al _0.7 Ga _0.3 As layer 32 (electron concentration = 3 × 10
¹⁷ cm ^-3 ) is formed to a thickness of about 2 μm, and a p-type Al _0.2 Ga _0.8 As layer 33 (hole concentration = 1.5 × 10 ⁷ cm ⁻¹ ) with a thickness of 2 μm is formed on top of it by adding Ge as an impurity. Forming the substrate
A diode having a hetero pn junction interface 34 formed by forming an electrode 35 on the 31 and p-type Al _0.2 Ga _0.8 As layer 33 was produced. This diode is a high-performance heterojunction diode in which the heterojunction interface and the pn junction interface match well as those shown in FIG. 2, and can be used as a light emitting element and a light receiving element.

The manufacturing method of this diode is a liquid phase epitaxial growth method using a conventional slide board, and the liquid phase preparation conditions are as shown in Table 1 below.
The Ga solution having the composition of is brought into contact with the n-type GaAs substrate 31 at 0.3 ° C.
The n-type Al _0.7 Ga _0.3 As layer 32 was grown by removing the Ga melt No. 1 liquid after slowly cooling at a speed of a minute, and then.
At 797 ° C, Ga melt No. 2 liquid in Table 1 was added to n-type Al _0.7 Ga _0.3 As layer 32
After contacting with the above and gradually cooling at the same rate as above, the Ga melt No. 2 liquid was removed to obtain p-type Al _0.2 Ga _0.8 As.
Grow layer 33. By attaching a suitable ohmic electrode (Au electrode) 35 to the crystal thus obtained, the heterojunction diode shown in FIG. 3 can be obtained.

Example 2 An example of a transistor manufactured by the method of the present invention will be described with reference to FIG.

As shown in Fig. 4, n-type GaAs substrate (electron concentration = 1 x 10
¹⁸ cm ^-3 ) 41 Non-doped n-type GaAs with no added impurities
A layer 42 (electron concentration = 1 × 10 ¹⁶ cm ⁻³ ) having a thickness of about 2 μm is formed, and a p-type Al _0.2 Ga _0.8 As layer 43 (hole concentration ~ 10 ¹⁸ cm ^-3 )
Is formed to a thickness of about 0.2 μm, and an n-type Al _0.4 Ga _0.6 As layer 44 (electron concentration ˜10 ¹⁷ cm ⁻³ ) doped with Ge as an impurity is further formed on this p-type layer 43 to a thickness of about 1 μm. Layer 44 to layer 44
Te to facilitate ohmic contact with
Forming an n-type GaAs layer 45 (electron concentration ˜10 ¹⁸ cm ⁻³ ), and forming an ohmic electrode 46 on each of the layers 45, 43 and 41, the n-type GaAs layer 42 being a collector and p-type Al. _0.2 Ga _0.8 As layer
43 base, n-type Al _0.4 Ga _0.6 As layer 44 emitter, n-type
This is an example of a transistor in which the GaAs layer 45 is used as an auxiliary layer for ohmic contact.

This transistor can be obtained by a conventional liquid phase epitaxial growth method using a slide boat, and by preparing a crystal under the liquid phase charging conditions for forming each layer as shown in Table 1. When describing each process in detail,
At 800 ° C., first, the Ga melt No. 3 liquid shown in Table 1 was brought into contact with the n-type GaAs substrate 41 and gradually cooled at a rate of 0.3 ° C./min.
The liquid is removed to grow the non-doped n-type GaAs layer 42, and then the Ga melt No. 4 liquid is added to the non-doped n-type GaAs layer 42 at 797 ° C.
It is contacted on the surface and slowly cooled at the above speed to remove the Ga melt No. 4 liquid to grow a Ge-doped p-type Al _0.2 Ga _0.8 As layer 43, and then at 798 ° C., the Ga melt No. 5 liquid is added to the Ge melt. It is brought into contact with the doped p-type layer 43 and gradually cooled at the above speed to remove the Ga melt No. 5 liquid, and grow a Ge-doped n-type Al _0.4 Ga _0.6 As layer 44, and subsequently at 796 ° C. The No. 6 solution is brought into contact with the Ge-doped n-type layer 44 and gradually cooled at the above speed to remove the Ga melt No. 6 solution and grow the Te-doped n-type GaAs layer 45 to obtain a target crystal. . By attaching an appropriate ohmic electrode (Au alloy) 46 to the crystal thus obtained, the heterojunction transistor shown in FIG. 4 can be formed.

In a transistor, the movement of the pn junction position affects the performance of the transistor as the base becomes thinner. Therefore, even if the thickness of the corner base is thin, p-
When the n-junction position is moved, the high frequency characteristic is deteriorated. In the transistor manufactured by the method of the present invention,
Since such movement of the pn junction position does not occur during crystal growth or subsequent heat treatment, high frequency characteristics can be achieved as designed.

〔The invention's effect〕

According to the present invention, when the crystal layer on the substrate is liquid-phase epitaxially grown, a predetermined amount of germanium, which is one kind of impurity, is added and the amount of aluminum is increased at a predetermined germanium concentration by having the structure as described above. In the liquid phase epitaxial growth characteristic curve in which the formed crystal layer changes from the p-type to the n-type with the minimum carrier concentration as the boundary, contact is made with a gallium solution containing a predetermined amount of aluminum on the side where the p-type is formed. P
Since the n-type layer is formed, and the n-type layer is formed by contacting with a gallium solution containing more aluminum than the predetermined amount of aluminum on the side where the n-type is formed, the n-type Al is formed.
A compound semiconductor device having a designed hetero pn junction in which the hetero junction of _x Ga _1-x As and the p-type Al _y Ga _1-y As and the pn junction interface coincide with each other can be obtained. Therefore, various compound semiconductor devices manufactured by using the method of the present invention have the following features. That is, a semiconductor laser having a hetero pn junction in a combination of AlGaAs / GaAs, AlGaAs / AlGaAs, etc.,
As a light emitting diode, a light receiving element, and a transistor, the pn junction position and the hetero junction position do not change even during high-temperature treatment during and after crystal growth, so high-efficiency minority carrier injection and high-efficiency carrier confinement can be performed. In this case, the luminous efficiency can be improved, the dark current can be reduced in the light-receiving element, and the transistor can be increased in width and higher in frequency.

[Brief description of drawings]

FIG. 1 shows Ge doping by liquid phase growth in the method of the present invention.
2 is a graph showing the characteristics of Al _x Ga _1-x As, FIG. 2 is a graph showing the relationship between the cross section of the pn junction of the compound semiconductor manufactured by the method of the present invention and the SEM observation signal, and FIG. FIG. 4 is a schematic sectional view of a diode manufactured by the method of the present invention, FIG. 4 is a schematic sectional view of a transistor manufactured by the method of the present invention, and FIG. 5 is a schematic sectional view showing a pn junction of a conventional AlGaAs. . In the figure, 1 ... p-type GaAs substrate 2 ... p-type AlGaAs layer 3 ... n-type AlGaAs layer 4 ... electrode 5 ... electromotive force signal peak 6 ... hetero interface

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01L 29/808 31/10 H01S 3/18 (56) References JP-A-56-129319 (JP, A) Japanese Patent Sho 49-25630 (JP, B1) Japanese Patent Sho 49-25629 (JP, B1)

Claims (3)

[Claims] 1. A substrate and n-type conductivity A formed by adding germanium (Ge) as an impurity formed on the substrate.
_x Ga _1-x As (0 <x <1) layer and A _y Ga _1-y As (0 <y <1) layer showing p-type conductivity (where x and y
Is in the relationship of 0 <y <x <1) and at least one pn junction of the compound semiconductor device, wherein both layers contain germanium as an impurity and aluminum (A) and arsenic. It is formed by liquid phase epitaxial growth of a crystal layer on a substrate by bringing it into contact with a gallium (Ga) solution containing (As), and in performing liquid phase epitaxial growth, an A _y Ga _1-y As layer Is a liquid phase epitaxial growth characteristic curve in which the crystal layer formed changes from the p-type to the n-type at the minimum carrier concentration when the amount of aluminum is increased at a predetermined germanium concentration. The A _x Ga _1-x As layer formed by contacting with a gallium solution containing a predetermined amount of aluminum on the side where the n-type is formed is formed. 2. The method for producing a compound semiconductor device, which is formed by contacting with a gallium solution containing an amount of aluminum larger than the predetermined amount of aluminum. 2. A first A _{x on} which a germanium having the same conductivity as that of a GaAs substrate is added as an impurity.
A Ga _1-x As (0 <x <1) layer is formed and a second A _y Ga _1-y As (0 <y <is added with germanium as an impurity having a conductivity different from that of the first layer. 1) a layer formed on the first layer, the GaAs substrate and A _y
The method of manufacturing a compound semiconductor device according to claim 1, wherein an electrode is formed on the Ga _1-y As layer. 3. A first A _x on a GaAs substrate doped with germanium having the same conductivity as the substrate as an impurity.
A Ga _1-x As (0 <x <1) layer is formed and a second A _y Ga _1-y As (0 <y <is added with germanium as an impurity having a conductivity different from that of the first layer. 1) A third A _z G layer formed on the first layer and doped with germanium having the same conductivity as the first layer.
a _1-z As (0 <z <1) layer (where y and z are 0 <
y <z <1) is formed on the second layer, and electrodes are formed on the GaAs substrate, the A _y Ga _1-y As layer and the A _z Ga _1-z As layer. A method of manufacturing a compound semiconductor device according to claim 1, wherein: