JPH06291068A - Liquid phase epitaxial growth method - Google Patents

Abstract

PURPOSE:To prevent solution for crystal growth from being left by growing a crystal of such a thickness as obtained at a specified deposition efficiency or above on a substrate. CONSTITUTION:A holding plate 13 has a recess 24 for holding a substrate crystal; the recess is designed to house a substrate 25 at its bottom. A second slider 12 is formed on the holding plate 13. The slider 12 is therein provided with narrow perpendicular paths 20a, 20b and 20c for melt dropping and reservoirs 21a, 21b and 21c perpendicularly connected therewith, respectively; the cross section of these paths and reservoirs shapes three L's. The height of the reservoirs is 3mm, 1mm and 3mm, respectively, which allows growth melt stored therein to be deposited on a substrate 25 at an deposition efficiency of 80% or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase epitaxial growth method for forming a liquid phase epitaxial layer such as a light emitting diode and a semiconductor laser.

[0002]

2. Description of the Related Art FIG. 2 shows a sliding board for carrying out liquid phase epitaxial growth which is generally used in the past.
It is a schematic sectional drawing which shows an example of G. 1 is a solution container, 2
Is a melt (solution) contained in each container 3, 4 is a slider movable in the arrow direction, and 5 is a recess containing a substrate 6 of uniform thickness for crystal growth. This growth method is 80
After being kept at a high temperature of 0 ° C., the slider 4 is moved to a position corresponding to the crystal growth substrate 6 and each solution while performing equilibrium cooling at a cooling rate of 0.2 ° C./min so that growth is performed. However, when using this method,
In the growth process of several layers, an entirely non-uniform growth layer is formed. In particular, the edges of the substrate tend to grow thick, which causes various adverse effects during the growth process of the crystal layer and the processing of the growth substrate.

To correct this, the substrate 6 is shown in FIG.
As shown in FIG. 3A, a step portion 6a is formed in advance at a location where it grows thick, or as shown in FIG.
There is one in which b is formed so that the surface of the growth layer becomes flat. FIG. 4A is a diagram showing a growth result when growing the substrate 6 having the shape shown in FIG. 3A, and FIG. 4B is a diagram corresponding to FIG. 3B. is there.

[0004]

However, in the case of FIG.
Even if the substrate 6 having the shape shown in FIGS. 3A and 3B is used, the solution remains on the stepped portion 6a and the inclined portion 6b and is mixed with the solution for growing on the upper surface, and the peripheral portion The crystal compositions of the above are mixed. In addition, when the slider 4 is slid, when the fine crystals formed in the solution slide, a part of the fine crystals arrives on the substrate, and the solution remains. Therefore, the present invention is to provide a liquid phase epitaxial growth method that eliminates such problems.

[0005]

The present invention has been made in view of the above problems, and it is an object of the present invention to provide the following method. That is, in a liquid phase epitaxial growth method in which a crystal growth solution is grown on a substrate by using a sliding boat, the crystal growth solution is grown on the substrate with a thickness of precipitation efficiency of 80% or more. A liquid phase epitaxial growth method characterized in that

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 (A) to 1 (E) are sliding board.
FIG. 3 is a process diagram for obtaining a crystal for a double heterostructure GaAlAs infrared light emitting diode according to the present invention. The sliding boat is made of graphite and has a first slider 11 and a second slider.
It has a three-layer structure including a slider 12 and a fixing plate 13.
The fixing plate 13 is provided with a recess 24 for fixing the substrate crystal, the depth thereof is 0.8 mm, and the substrate 25 is accommodated at the bottom thereof. The second slider 12 is slidably provided on the fixed plate 13, and thin vertical passages 20a, 20b, 20 for dropping the melt (solution) are provided.
c and the reservoirs 21a, 21b, which communicate with each other in the direction perpendicular to this
21c and 3c are respectively provided at three positions so as to have an L-shaped cross section. These reservoirs 21a, 21
The heights of b and 21c are 3 mm, 1 mm and 3 m, respectively.
The height is set to m so that the growth melt accumulated here can be grown on the substrate 25 at a deposition efficiency of 80% or more.

Then, on the upper surface side of the second slider 12,
A first slider 11 is provided so as to be slidable with respect to the second slider 12, and Ga, polycrystalline GaAs, Al and a drain are provided.
Melt reservoirs 14, 15 and 16 for accommodating the punts are provided respectively, and these shapes are funnel-shaped so that excess polycrystal does not drop into the growth melt in the reservoirs 21a, 21b and 21c during growth. The shape is narrowed down to.

With the sliding boat having such a structure, for example, the n-clad layer Ga _0.3 Al _0.7 As /
P active layer Ga _0.97 Al _0.03 As / P clad layer Ga _0.3
The process of growing Al _0.7 As will be described below with reference to the drawings. The growth thickness is required to be thick because it is necessary to remove the substrate in order to increase the luminous efficiency. However, the growth thickness cannot be increased infinitely. The thickness of the growth layer should be strong enough to withstand processing,
Since it has been empirically known that the total thickness of about 120 μm can be endured, it suffices to carry out the growth so as to obtain this thickness. Therefore, it is necessary to grow in consideration of this fact.

The melt reservoirs 14, 15 of the first slider 11
No. 16 has Al mixed crystal ratios of 0.7, 0.03 and 0.7, respectively.
The melt reservoirs 14 and 15 are filled with a predetermined P-type carrier concentration, and the melt reservoir 16 is filled with an appropriate amount of Zn and Te so as to obtain a predetermined N-type carrier concentration. Then, a P-type GaAs substrate 25 having a thickness of 300 μm is formed in the recess 24.
Set. The boat thus set is introduced into a reaction tube (not shown). After vacuuming, H ₂ reducing atmosphere gas is flowed at a flow rate of 31 / min. Next, after the temperature is raised to 900 ° C., the temperature is kept uniform for 2 hours (FIG. 1 (A)).

The melt holes of the melt reservoir 14 of the first slider 11 are overlapped with the passages 20a of the second slider 12 and the melt 17 is poured into the reservoir 21a. Further, the first slider 11 is shown in FIG.
(A) Melt 17 drawn in the melt reservoir 14 by pulling to the upper right
And disconnect. At this time, the melt holes of the melt reservoirs 15 and 16 are prevented from facing the vertical passages 20b and 20c (see FIG. 1).
(B)).

After the temperature is lowered by 3 to 5 ° C., both the first and second sliders move to the left in the drawing, and the growth melt 17 in the reservoir 21a is placed on the substrate 25 (FIG. 1C).

The first layer is grown by cooling to 800 ° C. at a cooling rate of 0.1 ° C./min. First slider 1
1 is moved to the right, and the melt reservoirs 15 and 16 are overlapped on the vertical passages 20b and 20c of the second slider 12 to melt 18,
19 is poured into the reservoirs 21b and 21c. Then, the first slider 11 is further moved to the right to separate from the melts 18 and 19 contained in the reservoirs 21b and 21c, respectively (see FIG. 1).
(D)).

After that, the first and second sliders are integrally moved to the left, and the melts 18 and 19 are sequentially moved onto the substrate 25 to grow the second and third layers. When the temperature reaches 750 ° C., the first and second sliders are further moved to the left to remove the melt from the substrate 25 and cool it to room temperature (see FIG. 1).
(E)).

In this way, a good crystal layer having a uniform composition with no melt residue on the grown surface layer was obtained.
The thicknesses of the P-clad layer, P-active layer and n-clad layer were 125 μm, 0.2 μm and 10 μm, respectively.
The growth thickness of the edge portion of the substrate is as thick as 250 μm, but the recessed portion 24 of the substrate is as deep as 0.8 mm, and when the second slider 12 slides, it hits an abnormal growth portion of the edge portion, or fragments thereof remain on the substrate. Or, the growth layer is not scratched. Further, the substrate recess 24 is deep and the melt does not remain on the entire growth surface. This is because the heights of the reservoirs 21a, 21b, 21c are 3 mm and 1 mm, respectively, as described above.
mm and 3 mm, and the growth melt is 80% on the substrate 25.
This is because the growth is performed with the above precipitation efficiency.

This will be described in more detail. The precipitation efficiency indicates the ratio of the solute dissolved in the growth melt to crystallization, and this relationship is expressed by the following equation. η = S · ρ ₀ · d ₀ / ρ ₁ · d ₁ where η: precipitation efficiency S: solubility ρ ₀ : solvent density ρ ₁ : crystal density d ₀ : crystal thickness d ₁ : growth melt thickness

From this relational expression, it can be seen that the deposition efficiency decreases as the growth melt thickness increases. This is because as the thickness of the growth melt increases, the degree of supersaturation increases when the temperature is cooled by the same amount, so that precipitation on the graphite facing the substrate also easily occurs. Once the growth begins, the first grown crystallites become nuclei and grow and grow one after another. In the remaining melt on the substrate, the bond between graphite and this microcrystal is weak, so part of it drops into the growth melt and arrives on the substrate due to vibration and resistance of the melt when the slider is moved. It is thought to occur because it stays. In order to prevent this, it is necessary to suppress the growth of fine crystals deposited on graphite, that is, to improve the deposition efficiency.

From the above, when the melt thickness is reduced to improve the deposition efficiency to 80% or more, there is no melt residue on the substrate, and the minimum amount is required for complete removal of the melt residue on the substrate. It has been confirmed that a deposition efficiency of 80% is required. The reason why the melt thickness is changed depending on the composition growth melt is that the solubility of As is different depending on the composition, and thus the degree of supersaturation is different. That is, since the composition of the active layer is close to that of GaAs and the degree of supersaturation is large, it is necessary to reduce the thickness of the melt, so that the thickness is reduced. In the case of growth from a melt having a high degree of supersaturation, it can be said that if the melt thickness is made thin, growth with high precipitation efficiency becomes possible and a crystal layer having a stable composition with no melt residue can be obtained. In the present embodiment, a specific example of the GaAs-based growth method has been described, but it goes without saying that it can also be applied to the InP-based growth method.

[0018]

According to the present invention, the solution for crystal growth remaining on the substrate can be completely removed, and crystals of a uniform growth layer can be obtained. Further, there is an effect that abnormal growth cannot be performed at the end portion of the substrate, and complicated processing is unnecessary.

[Brief description of drawings]

FIG. 1 is a process drawing for obtaining a crystal for a double heterostructure GaAlAs infrared light emitting diode by a sliding boat.

FIG. 2 is a schematic sectional view showing an example of a sliding boat for performing conventional liquid phase epitaxial growth.

FIG. 3 is a diagram showing a shape of a substrate used in a conventional method.

FIG. 4 is a corresponding diagram showing a growth layer when the substrate shown in FIG. 3 is used.

[Explanation of symbols]

 11 First Slider 12 Second Slider 13 Fixing Plate 14, 15, 16 Melt Reservoir 17, 18, 19 Melt (Solution) 20a, 20b, 20c Vertical Passage 21a, 21b, 21c Reservoir 24 Concave 25 Substrate

Claims (1)

[Claims] 1. A liquid phase epitaxial growth method in which a crystal growth solution is grown on a substrate using a sliding boat, wherein the crystal growth solution is grown on the substrate at a thickness with a deposition efficiency of 80% or more. A liquid phase epitaxial growth method characterized in that it is performed.