JPH0361636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for epitaxial growth of semiconductor crystals.

[Conventional technology and problems]

Conventionally, in the liquid phase epitaxial growth method of semiconductor crystals, a temperature difference is given to at least one solution in which a growth material is dissolved, and the growth material is placed on a slider that is moved linearly or circularly in one direction. A temperature difference method is widely known in which a semiconductor crystal is epitaxially grown on a substrate crystal by bringing a mounted substrate crystal into contact with the low-temperature side of these solutions and holding it for a certain period of time.

In this temperature difference method, the
Al and GaAs and Zn as doping impurity,
A Ga solution containing Te, etc. is placed in the solution reservoir of a graphite container holder and kept at a high temperature, and a temperature gradient is applied so that the temperature decreases toward the bottom of the solution. The substrate crystal inserted into the recess is kept in contact with the lower side of the solution in the container reservoir for a certain period of time. In this way, the supersaturated component in the Ga solution is precipitated onto the substrate crystal, whereby a Ga _1-x Al _x As semiconductor crystal is epitaxially grown on the substrate crystal.

Here, the growth of Ga _1-x Al _x As semiconductor crystal for a desired x can be determined from the liquidus line and solid phase composition line graph shown in Fig. This can be achieved by selecting the amount and growth temperature.

However, in the temperature difference method mentioned above,
The background concentration N _A of the acceptor during non-doped growth is 1 x 10 ¹⁷ /cm ³ or more, which reduces the impurity concentration in p-GaAlAs and n-GaAlAs (normally both N _A and N _D are 10 ¹⁷ /cm ^{3 ).} (which is on the order of
It becomes shaped like i-n.

[Purpose of the invention]

In view of the above points, the present invention accurately controls the impurity concentrations N _A and N _D by lowering the background concentration and appropriately adjusting the amount of impurities added as acceptors or donors. It is an object of the present invention to provide a method for liquid phase epitaxial growth of semiconductor crystals.

[Means and actions for solving problems]

According to the present invention, the above object is achieved by
By bringing a substrate crystal placed on a slider into contact with a Ga solution containing GaAs, Al, etc. and holding it for a certain period of time, a Ga _1-x Al _x As semiconductor crystal is epitaxially grown on the substrate crystal. In the liquid phase epitaxial growth method of semiconductor crystals,
This is achieved by adding In to the above solution at a weight ratio of In/Ga of 1.0 or more.

According to this invention, since In, which is an electrically inactive element, is added to the Ga solution at a weight ratio of 1.0 or more to Ga, the added In does not dope into the growth layer. By preventing the intrusion of undoped C, the background concentration N _A during non-doped growth of the acceptor can be reduced to 1×10 ¹⁵ /cm ³
Therefore, it is possible to accurately adjust the amount of impurity added as a donor or acceptor. This allows the impurity concentrations N _A and N _D to be accurately controlled, thus resulting in a pn junction in which the concentration change near the interface is accurately rectangular.

〔Example〕

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of a liquid phase epitaxial growth apparatus for carrying out the present invention.
0 is a plurality of solution reservoirs 12a (first
(see Figure A), and a solution 1 in each solution reservoir 12a at the bottom of the solution holder 12.
1 and a substrate holder 14 on which a substrate crystal 13 is placed in contact with the substrate crystal 13.

The substrate holder 14 has a plurality of recesses 14a arranged in the upper surface thereof, and is adapted to hold the substrate crystal 13 while being inserted into the recesses 14a. Further, the solution holder 12 and the substrate holder 14 are driven to rotate intermittently relative to each other by appropriate means, whereby a semiconductor crystal is epitaxially grown on the substrate crystal 13 inserted into the recess 14a of the substrate holder 14. It's becoming like that. The above configuration is similar to that of a conventional liquid phase epitaxial growth apparatus.

In the present apparatus 10, crystal growth is performed by adding In to a Ga solution in which semiconductor materials GaAs and Al are dissolved, as a solution 11 placed in a solution reservoir 12a, at a weight ratio of In/Ga of 1.0 or more.

The present apparatus 10 is configured as described above, and when growing a crystal on the substrate crystal 13, the substrate crystal 1 is grown in the same manner as a conventional liquid phase epitaxial growth apparatus.
A growth layer of Ga _1-x Al _x As semiconductor crystal can be grown on the substrate 3, and the background concentration N _A during non-doped growth of the acceptor can be reduced. This is because the In added to the solution 11 is electrically inactive, so that the unintentionally added C impurity, which can be electrically activated, invades the growth layer of the semiconductor crystal during crystal growth. This is thought to be due to the fact that the added In suppresses this.

The present apparatus 10 has a solution reservoir 12a of the solution holder 12 and a substrate holder 14 as shown in FIG.
It is clear that the same effect can be obtained by a configuration in which the recesses 14a are arranged in a line.

FIG. 3 shows that according to the method according to the invention,
This figure shows the results of measuring the background concentration N _A for the weight ratio In/Ga when In is added to a Ga _1-x Al _x As semiconductor (x=0.8). According to this graph, it is clear that the background concentration N _A decreases as the weight ratio In/Ga increases, and the background concentration N _A decreases to 10 ¹⁵ / around the weight ratio In/Ga = 1.0. It has decreased to the order of ^cm3 .

〔Effect of the invention〕

As described above, according to the present invention, semiconductor materials
By bringing a substrate crystal placed on a slide into contact with a Ga solution in which GaAs and Al are dissolved and holding it for a certain period of time, a Ga _1-x Al _x As semiconductor crystal is epitaxially grown on the substrate crystal. In the liquid phase epitaxial growth method of semiconductor crystals,
In, an electrically inactive element, is added to the Ga solution.
Since it is added at a weight ratio of 1.0 or more to Ga, this added In prevents undoped C from entering the growth layer, thereby reducing the background concentration N _A during non-doped growth of the acceptor. It becomes possible to reduce the impurity to 1×10 ¹⁵ /cm ³ or less, and therefore the amount of impurity added as a donor or acceptor can be adjusted accurately. This allows the impurity concentrations N _A and _ND to be accurately controlled.

[Brief explanation of drawings]

Fig. 1 shows an example of a liquid crystal epitaxial growth apparatus for carrying out the present invention, A is an exploded view, B is a schematic perspective view, Fig. 2 is a schematic cross-sectional view showing another embodiment, and Fig. 3 is a schematic perspective view. FIG. 4 is a graph showing the background concentration N _A versus the weight ratio In/Ga, and FIG. 4 is a graph showing the liquidus line and solid phase composition line. 10...Liquid phase epitaxial growth apparatus, 11...
...Solution, 12...Solution holder, 12a...Solution reservoir, 13...Substrate crystal, 14...Substrate holder,
14a... recess.

Claims (1)

[Claims] 1. By bringing a substrate crystal placed on a slider into contact with a Ga solution containing semiconductor materials such as GaAs, Al, etc. and holding it for a certain period of time,
In a liquid phase epitaxial growth method for semiconductor crystals in which a Ga _1-x Al _x As semiconductor crystal is epitaxially grown, In is added to the solution in a weight ratio
A liquid phase epitaxial growth method for semiconductor crystals characterized by the addition of In/Ga of 1.0 or more.