JPS62202893A - Liquid phase epitaxy - Google Patents

Abstract

PURPOSE:To make it possible to grow an epitaxial layer having improved uniformity and reproducibility even for a film thickness of <=1mu, by setting the length of an opening part of a solution reservoir in the sliding direction of a substrate holder according to the film thickness of the epitaxial layer to be grown. CONSTITUTION:The length of an opening part of a solution reservoir in the sliding direction of a substrate holder can be set according to the film thickness of an epitaxial layer to be grown. The solution reservoir having such an opening part may be provided in a solution holder to control the contact time of a solution for growth in the solution reservoir with a substrate even by sliding the substrate holder at a constant speed. For example, the solution reservoir having a short opening part in the sliding direction of the substrate holder may be provided in the solution holder for forming a thin-walled epitaxial layer. Thereby the contact time of the solution for growth with the substrate can be shortened and the aimed thin epitaxial layer is gown on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth method, and particularly to a method for epitaxial growth using a slide boat method.

[Prior art] Epitaxial growth methods for compound semiconductors such as GaAS include liquid phase epitaxy, vapor phase epitaxy (VPE), metal organic pyrolysis vapor phase epitaxy (MOCVD), and single molecule beam epitaxy (
MBE method), etc., but the liquid phase growth method is most suitable for obtaining a high-quality crystalline phase, and is widely used at the production level of light emitting diodes and semiconductor lasers. This liquid phase growth method is a method of growing crystals by bringing a substrate into direct contact with a solution containing component elements, and can be further divided into various methods depending on how the substrate is brought into contact with the solution. The third among them
The slide boat method shown in the figure is commonly used.

That is, the substrate 32 is fitted into a substrate holding recess formed on the surface of the substrate holder 31, and the substrate 32 is slid together with the substrate holder 31 between the pedestal 33 and the melt holder 34, and the substrate 32 is inserted into the melt holder. It is located directly below the growth solution 36 contained in the solution reservoir 35 of 34. Note that the solution reservoir 35 has a dimension approximately equal to the dimension d of the substrate 32. In this way, contact is made between the substrate 32 and the growth solution 36, and a high quality crystal layer is formed on the substrate 32.

[Problems to be Solved by the Invention] For example, in the case of a GaAs Schottky diode, a buffer layer with a thickness of 2 to 10 μm is grown on a single GaAs plate, and a layer of 0.2 to 0.3 μm is grown on the buffer layer. It is necessary to grow an active layer with a thickness of 0.2 to 0.2 to 0.0, since the thickness of this active layer directly affects the characteristics of the diode.
It is necessary to grow a thickness of 3-mm thick with good uniformity and reproducibility.

In addition, in the case of semiconductor lasers, the thickness of the active layer sandwiched between the cladding layers is as thin as 0.054 mm, and the yield of semiconductor lasers depends on how uniformly and reproducibly this thickness can be grown. is determined.

Conventionally, when growing thin layers such as the active layer of these Schottky diodes or the active layer of semiconductor lasers by the liquid phase epitaxial method, the substrate 32 in FIG.
Methods such as sliding the growth solution under the solution reservoir 35 at high speed and controlling the degree of supersaturation of the growth solution 36 in a complicated manner have been adopted. However, in this liquid phase epitaxial method, MB
The growth rate is faster than the E method or MOCVD method, and the thickness is 1.
It has been difficult to uniformly grow an epitaxial layer of p or less with good reproducibility.

Furthermore, although a slow cooling method is usually used in the liquid phase epitaxial method, it is difficult to grow a thin epitaxial layer on top of a thick epitaxial layer grown using this slow cooling method. That is, while growing a thick epitaxial layer, the temperature inside the furnace decreases, and the degree of supersaturation of the growth solution for the subsequently grown thin epitaxial layer increases. As a result, the growth rate increases,
It becomes impossible to control the thickness of thin layers.

Thus, an object of the present invention is to provide a liquid phase epitaxial growth method that solves the problems of the prior art described above and can grow an epitaxial layer with excellent uniformity and reproducibility even with a film thickness of about 11 JIR or less. be.

[Means for Solving the Problems] In order to achieve the above object, the liquid phase epitaxial growth method of the present invention adjusts the opening of the solution reservoir in the sliding direction of the substrate holder depending on the layer thickness of the epitaxial layer to be grown. This allows you to set the length of .

[Function] By providing a solution reservoir with an opening as described above in the solution holder, it is possible to control the contact time between the growth solution in the solution reservoir and the substrate even if the substrate holder is slid at a constant speed. can. For example, when a thin epitaxial layer is to be formed, a solution reservoir having a short opening in the sliding direction of the substrate holder may be provided in the solution holder. With this shift, the contact time between the growth solution and the substrate can be shortened, and a thin epitaxial layer can be grown on the substrate.

Therefore, by providing a plurality of solution reservoirs having openings of desired sizes in the solution holder, it is possible to perform multilayer growth of thin films or multilayer growth of thick films and valve membranes on the substrate.

[Example code] Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram of a slide boat for a double hetero type semiconductor laser used in a liquid phase epitaxial growth method according to an embodiment of the present invention.

The solution holder 1 has a cladding layer solution reservoir 2. Active layer solution reservoir 3. Cladding layer solution reservoir 4 and kill tube solution reservoir 5
is provided, and the substrate holder 7 is configured to be able to slide between the solution holder 1 and the pedestal 6.

The length of the board holder 7 in the sliding direction is 20III11.
1. A rectangular board holding recess with a length of 35 mm in the direction perpendicular to the board is provided.

In addition, solutions KII2 and 4 for the cladding layer of the solution holder 1
The cap layer solution reservoir 5 faces the substrate holder 7 and has a rectangular opening having a length of D1=ZOS in the sliding direction of the substrate holder 7 and 35all in the direction perpendicular thereto. On the other hand, the active layer solution reservoir 3 faces the substrate holder 7 in the sliding direction of the substrate holder 7 with D2=21111.
11. In the direction perpendicular to this, there is a groove-shaped frontage having a length of 35 InIR.

Epitaxial growth was performed using a slide boat with such a configuration.

First, 40 g of Ga, 3 g of GaAs, and Af for the cladding layer were placed in the solution reservoir 2 of the solution holder 1 as a growth solution.
137tq, 8g of Ga for active layer in solution reservoir 3, G
aAs O, 6g, A11, ll1g, Ga40g for cladding layer in solution reservoir 4, GaAs39, Afl,
371R9, Ga409 for Ki 17'/B layer in solution reservoir 5
.

3 g of GaAs was accommodated in each, and a 20×35ffi substrate 8 was fitted and held in the substrate holding recess of the substrate holder.

Next, this slide boat was placed in a reaction tube (not shown), and after replacing the inside of the reaction tube with hydrogen gas, the temperature was raised to 800° C. using an external electric furnace (not shown). After the temperature inside the furnace stabilized at 800°C, the temperature inside the furnace was lowered at a cooling rate of 0.5"C/min, and when the temperature reached 796°C, that is, the growth solution was made to have a degree of supersaturation of 4°C. By the way, the substrate holder 7 was slid, the substrate 8 was positioned directly below the solution reservoir 2 of the solution holder 1, and the sliding of the substrate holder 7 was stopped.

In this way, the substrate 8 was brought into contact with the growth solution in the solution reservoir 2, and a cladding layer (GaM 85ffl) with an M mixed crystal ratio of 0.35 was grown on the substrate 8. The substrate 8 is passed under the solution reservoir 3 by sliding it at a speed of 5 cm and 7 seconds, and M is deposited on the surface of the cladding layer.
An active layer (08M63 layers) with a mixed crystal ratio of 0.05 was formed.

Further, slide the substrate holder 7 and stop the substrate holder when the substrate 8 is located directly below the solution reservoir 4,
A second cladding with an M mixed crystal ratio of 0.35 is formed on the surface of the active layer.
id (08M63 layers) was formed. Similarly, the substrate holder 7 is slid to position the substrate 8 directly below the solution reservoir 5, and a cap layer (GaA
S layer> was grown in layers.

Epitaxy 1 for the double hetero type semiconductor laser formed as described above! Open the Leweba in half and open it at an angle of 5°.
After performing oblique polishing, etching was performed, and the epitaxial layer interface was measured with a SEM to examine the uniformity of the film thickness.

As a result, the thickness of the active layer was 0.062℃m±0.007
-, and it was possible to grow an extremely thin layer with good uniformity within the plane.

In addition, in the above example, only one solution reservoir with a groove-shaped opening was provided, and only an extremely thin active layer was formed.
By providing a plurality of solution reservoirs 21 having groove-shaped openings in the solution holder 22 as shown in FIG. 2, it becomes possible to form a multilayer structure of thin film epitaxial layers on the substrate 23. That is, formation of a superlattice structure by the liquid phase epitaxial growth method is realized.

Note that the method of the present invention is applicable to compound semiconductors of the ■-V group containing GaAs, mixed crystal compound semiconductors such as GaMAs, and I[-IV
It can be applied to liquid phase epitaxial growth of group compound semiconductors and their mixed crystals.

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects are exhibited.

(1) By setting the length of the opening of the solution reservoir in the sliding direction of the substrate holder according to the thickness of the epitaxial layer to be grown, even epitaxial layers with a thickness of about 1JJM or less can be improved. It can be grown with good reproducibility.

(2) Therefore, the present invention is particularly effective in manufacturing devices such as Schottky diodes and semiconductor lasers that require high quality and highly uniform thin films, and can improve device yield.

(3) Furthermore, by growing multiple layers of thin films, a superlattice structure can be formed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a slide boat used in a liquid phase epitaxial growth method according to one embodiment of the present invention, FIG. 2 is a block diagram of a slide boat used in another embodiment, and FIG. FIG. 2 is a configuration diagram of a slide boat used in a conventional example. In the figure, 1 is a solution holder, 2 to 5 are solution reservoirs, 7 is a substrate holder, and 8 is a substrate.

Claims (2)

[Claims] (1) After storing the growth solution in the solution reservoir of the solution holder and holding the substrate in the substrate holder, slide the substrate holder against the solution holder and place the substrate and the growth solution at the opening of the solution reservoir. A liquid phase epitaxial growth method characterized in that the length of the opening of the solution reservoir in the sliding direction of the substrate holder is set depending on the layer thickness of the epitaxial layer to be grown. Method. (2) a plurality of the solution reservoirs are provided in the solution holder;
2. The liquid phase epitaxial growth method according to claim 1, wherein multiple epitaxial layers are grown on the substrate as the substrate holder is slid.