JPH034521A - Liquid phase crystal growth method - Google Patents

Abstract

PURPOSE:To prevent decomposition and contamination of a substrate occurring from a volatile component, and to reduce the compositional change of the grown crystal occurring from evaporation of volatile component by a method wherein the evaporation of the undesirable component in the volatile ingredient contained in a solvent material is suppressed using a liquid sealing compound. CONSTITUTION:An N-type GaAs current blocking layer 52, a P-type AlxGa1-xAs first clad layer 43, a GayIn1-yAszP1-z active layer, an N-type AlxGa1-xAs second clad layer 55, and an N-type GaAs ohmic contact layer 56 are laminated on a P-type GaAs substrate 51 successively. At this point, a stripe form groove 57 is provided on the surface of the substrate 51. Through the above-mentioned procedures, a graphite boat 31 is composed of a liquid solution holder 32 and a sliding plate 33 in order to conduct a liquid growth operation, a rectangular recess 34 is provided on the sliding plate 33 positioned on the lower part, and the substrate 51 is housed therein. Also, a plurality of solution reservoirs 36 to 39 are provided on the upper surface of the holder 32, and solution materials 40 to 43, containing liquid sealing compound 45 with which the vapor generated in the solvent basins will be blocked, are housed therein.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a liquid phase crystal growth method, and in particular, a method suitable for liquid phase crystal growth containing a material with a high vapor pressure in a raw material solution. This invention relates to a liquid phase crystal growth method.

(Prior Art) The basic structure of a semiconductor laser or a light emitting diode is formed by stacking a plurality of compound semiconductor single crystals having mutually different compositions.

When creating such a layered structure using the liquid phase crystal growth method, a melt holder with multiple solution reservoirs for forming multiple layers with different compositions, and each melt holder A graphite boat (mul
A triple-bin graph (He boat) is used.

FIG. 3 is a sectional view showing such a conventional graphite boat 1, and an outline of the liquid phase crystallization method using this graphite boat 1 will be explained below.

The main parts of the graphite boat 1 include a melt holder 2 and a slide plate 3. In this melt holder 2, three solution reservoirs 4.5.6 are bored in a straight line, and on the bottom surface of this melt holder 2, in the drilling direction of each solution reservoir 4.5.6. The slide plate 3 is inserted so as to be linearly movable along the line.

A recess 7 is formed on the upper surface of the slide plate 3, and a substrate 8 made of a semiconductor single crystal is housed in the recess 7.

The solution reservoir 4.5.6 contains the solution materials 9.10, 11 necessary to create a solution of the appropriate composition. During crystal growth, the entire boat 1 is inserted into a quartz furnace core tube through which hydrogen flows, and the temperature is raised to a desired temperature.

The substrate 8 accommodated in the slide plate 3 is separated from the solution reservoir 4.5.6 of the melt holder 2 during the heating period of the quartz tube and the period necessary for the entire system to reach thermal equilibrium. After the heating of the quartz tube is completed and the entire system reaches thermal equilibrium, the slide plate 3 is moved from the outside of the quartz tube using the quartz operating rod 12, and the substrate 7 is moved into the three solution reservoirs 4. 5.6 A predetermined crystal is grown on the substrate 7 by sequentially inserting it into the bottom surface. At this time, by appropriately selecting the composition and temperature schedule of the solution material 9.10°11 contained in the solution reservoir 4.5.6, a crystal layer with a desired composition and thickness is laminated on the substrate 7. be able to.

By the way, if there is a substance with a high vapor pressure in the solution material 9.10.11, evaporation of the material becomes a problem in the temperature raising step in the above process. If I were to give a specific example, AJ2
When growing GaAs (0≦X≦1) x l-x , p-type dopant Mg or Zn5
Evaporation of n-type dopants such as Te may become a problem. That is, (1) these elements escape from the solution into the atmospheric gas, and the doping amount of the resulting crystal becomes lower than the set value.

■The dopants that escaped into the atmospheric gas dissolve into other solutions again and contaminate them.

(2) The dopant that escaped into the atmospheric gas may reach the substrate surface, adhere to it, and further diffuse into the interior from the substrate surface.

Problems such as this arise.

To avoid this problem, conventionally each solution reservoir 4.5.6
Place a cover 13.14.15 over each solution reservoir 4.
5.6 is being sealed. however,
Even if the cover 13, 14, 15 is used in this manner, it is difficult to completely prevent the evaporation of the material, and this may cause problems in the case of crystal growth that is sensitive to evaporation.

FIG. 4 is a diagram showing a semiconductor laser as an example of a crystal structure manufactured by a conventional liquid phase crystal growth method. The figure shows the structure of a conventionally known visible light semiconductor laser (KIsh1no et al. JEERJOURNAL
OF QLIANTUM ELECTRONIC9,V
OL, QE-23, NO, 2, PEBRUARY 19
87. P, 180), this structure has an n-type AJ2GaAs first cladding layer 2 on an n-type GaAs single crystal substrate 21.
2. A Ga1nAsP active layer 23, a p-type A, gGaAs second cladding layer 24, and a p-type GaAs ohmic contact layer 25 are laminated in this order.

When manufacturing this semiconductor laser, a graphite cover 13.14.1 is placed over each solution reservoir 4.5.6 in order to prevent evaporation of P from the growth solution material of the active layer 23.
5, but nevertheless, the evaporated P is
The surface of the aAs substrate 21 is contaminated.

Therefore, in order to remove this contamination, the surface of the substrate is melted back. Also,
Another conventional example of a similar crystal growth system is the structure of a semiconductor laser shown in FIG.
Appl, Phys, Lett, 4B(5), 1Mar
ch L985. P, 455).

The compositions of the substrate 61, the first cladding layer, the active layer 63, the second cladding layer 64 and the ohmic contact layer 65 are the same as the corresponding parts 21.22.23.24.25 of the structure shown in FIG. . However, in this example, the sign of the conductivity is reversed, the n-type GaAs current blocking layer 66 is present, and there is a groove 67 reaching from the surface of the current blocking layer 66 into the substrate 61, so that the active layer 63 is curved. What they do is different. In this example, the P vapor accelerates the decomposition of GaAs on the substrate surface, resulting in the problem that the shape of the groove 67 is deformed. In addition, the composition of the raw material solution becomes insufficient in P than the set value,
Since the composition of the resulting crystal also deviates from the set value, the difference in lattice constant (so-called misfit) between the active layer 63 and GaAs, which is the material of the substrate 61, tends to increase. A larger misfit is the active layer 63.
This results in larger residual stress and accelerates the deterioration of the semiconductor laser. When the misfit exceeds a certain limit value, normal crystal growth becomes difficult.

(Problems to be Solved by the Invention) As mentioned above, in the conventional liquid phase crystal growth method in which the solution reservoir is covered with a cover made of a solid material such as graphite, evaporation of volatile components in the raw material solution cannot be sufficiently prevented. This volatile component causes contamination and decomposition of the substrate surface, causing defects in the grown crystal. In addition, the controllability of the composition of the grown crystal is poor, resulting in an increase in unnecessary misfit between the crystal and the substrate.

The present invention was made to solve the above-mentioned conventional problems, and can completely suppress the evaporation of volatile components in the raw material solution, thereby preventing contamination and decomposition of the substrate surface due to volatile components, and an increase in misfit. It is an object of the present invention to provide a liquid phase crystal growth method that can suppress the growth of crystals and achieve high-quality crystal growth with good yield.

[Structure of the Invention] (Means for Solving the Problems) The liquid phase growth method of the present invention melts a solution material made of a predetermined material accommodated in a plurality of solution reservoirs of a solution holder,
In a liquid phase crystal growth method in which substrates are successively brought into contact with this molten solution material and predetermined compound semiconductor crystals are sequentially laminated on this substrate, vapor generated from the solution material covers the surface of the solution material when the solution material is melted. The method is characterized in that crystal growth is performed by making the solution material contain a liquid sealing material that blocks .

(Function) Since the liquid sealant completely covers the free surface of the molten solution material, it can completely prevent the vapor from the solution material from scattering. Therefore, it is possible to prevent contamination of the substrate surface or decomposition of the substrate surface due to this vapor, and it is also possible to prevent fluctuations in the solution composition due to scattering of the solution material or remixing of the vapor into other solution materials. Controllability of the composition or doping amount of the crystal obtained by growth is improved, and high-quality crystal growth can be performed with good yield.

(Example) Hereinafter, an example of the method of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a graphite boat used in the example method.

The main parts of the graphite boat 31 made of high-purity carbon graphite include a melt holder 32 and a slide plate 33. There is. A rectangular recess 34 is formed in the slide plate 33, and a substrate 35 is accommodated in the recess 34.

A plurality of, for example, four solution reservoirs 36, 37, 38, 39 are bored in the upper surface of the melt holder 32, and a solution material 40 of a predetermined composition is placed in these solution reservoirs 36, 37, 38, 39. .41, 42, and 43 are accommodated. Also,
An operating rod 44 for moving the slide plate 33 is provided at one end of the slide plate 34.

A method of manufacturing the visible light semiconductor laser shown in FIG. 2 using the boat 31 having such a configuration will be described below.

The visible light semiconductor laser shown in FIG. 2 includes a p-type GaAs substrate 51, an n-type GaAs current blocking layer 52, a p-type AJ2
GaAs first cladding layer 53, x 1
-X Ga In As P active layer 54, n-type Y i-y z 1-z AJ2 Ga As second cladding layer 55, n-type x
1-X GaAs ohmic contact layers 56 are sequentially laminated (in the example, X-0, 7, y-0, 51, 2-0
, 03), striped grooves 57 are formed on the surface of the substrate 51.
is formed.

The n-type GaAs current blocking layer 52 acts as a current blocking layer of this semiconductor laser device structure, and the striped grooves 52
7 acts as a path for driving current. At the same time, the striped grooves 57 serve to limit the transverse mode of the semiconductor laser. When forming the striped grooves 57, which have such an important role, it is important to control the groove shape with high accuracy in order to maintain good device characteristics.

However, in the conventional method, the striped grooves were deformed due to decomposition of the substrate surface by P vapor generated from the solution material, and the shape could not be controlled.

In this embodiment method, a p-type GaAs substrate 5 is grown by liquid phase crystal growth using a graphite boat 31 shown in FIG.
1, an n-type GaAs current blocking layer 52, a p-type A, g
Qa As first cladding layer 5x 1-x 3, Ga In As P active layer 54,
The ny l-y z 1-z type AJ2 GaAs second cladding layer 55 and the n-type X 1-x GaAs ohmic contact layer 56 are sequentially laminated.
．． Solution materials 40, 41, 42, 43 corresponding to each of the above layers are stored in 37, 38, 39. The material components of each of these solutions are shown in Table 1 below.

A solution material 41 corresponding to the active layer 54 of the semiconductor laser is contained in the solution reservoir 37.
contains P, which is an element with high vapor pressure. The solution material 41 in the solution reservoir 37 is covered with a solution layer of a liquid sealant 45 filled with the purpose of preventing evaporation of P.

As this liquid sealant 45, boron sesquioxide (B203) was used in this embodiment. The specific gravity of this boron oxide is about 1.5, which is smaller than the specific gravity of the solution material 41, which is about 7. Therefore, there is no need to take any special measures, and if the temperature is raised to 15fi, 4° C. or higher, which is the melting point of In, which is the solvent of the solution material 41, the liquid sealing material 45, which is boron oxide, can be applied to the upper surface of the solution material 41. Floating on. Further, if the temperature is further increased to a temperature slightly higher than the melting point of the liquid sealant 45 of a little less than 500° C., the liquid sealant 45 melts and covers the upper surface of the solution material 41 . Since this liquid sealing material 45 has a high viscosity near its melting point, it was desirable to keep the temperature at 700° C. or higher to ensure complete sealing. Under these circumstances, the liquid phase crystal growth temperature was set at 790°C.

That is, in the method of this embodiment, the entire graphite boat 31 shown in FIG. 1 is inserted into a quartz furnace core tube through which hydrogen flows, and the temperature is raised to 792°C.

Then, the graphite boat 31 is left at this temperature for one hour to allow the entire system of the graphite boat 31 to reach thermal equilibrium. Next, by lowering the temperature by 2° C., supersaturation is formed in each solution material 40, 41, 42, and 43. In this state, the quartz operating rod 44
A predetermined crystal is grown on the substrate 35 by moving the slide plate 33 using a slider and sequentially inserting the substrate 35 into the bottom surfaces of the four types of solution materials 40, 41, 42, and 43.

The thickness of each crystal layer at this time is controlled by appropriately selecting the growth time. For example, in the case of the active layer 54, a thickness of about 0.1 μm was obtained with a growth time of 5 seconds.

In the method of this embodiment, significant deformation of the striped grooves 57 caused by decomposition of the substrate surface due to the action of evaporated P does not occur, and as a result, the liquid sealing material 45 for sealing the P vapor does not The effect was confirmed.

Moreover, the average value of the oscillation wavelength of the semiconductor laser device thus obtained within the same web was within ±1.5 rv between liquid ill crystal growth lots. This value was less than half of the value when no liquid sealant was used, and this also confirmed the effectiveness of the liquid sealant in sealing P vapor.

In addition, in the above-mentioned example, Te, M used as a dopant
Since the evaporation of g could be ignored, no measures were taken to prevent evaporation for the solution materials 40, 42, and 43 other than the solution material 41, but using the liquid sealant 45 for these also has the effect. Of course.

Further, the liquid sealing material 45 is not limited to boron sesquioxide used in this embodiment, as long as it is a material that satisfies the following four properties. That is, (1) it becomes a liquid with sufficiently low viscosity at the liquid phase crystal growth temperature;

■It is stable at liquid phase crystal growth temperatures and does not significantly react with the raw material solution, boat material, or atmospheric gas.

■The specific gravity is smaller than that of the raw material solution.

■Do not transmit the volatile components of interest.

It is.

[Effects of the Invention] As explained above, according to the liquid phase growth method of the present invention,
The liquid encapsulant suppresses the evaporation of undesirable volatile components in the solution material, prevents decomposition and contamination of the substrate caused by these volatile components, and further reduces the composition of the growing crystal caused by this evaporation. Fluctuations can be reduced. , From these facts, it becomes possible to perform high-quality crystal growth with good yield.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a liquid phase crystal growth system including a graphite boat used in an example of the method of the present invention, and FIG. The third factor is a cross-sectional view to explain a liquid phase crystal growth system including a graphite boat according to the conventional method. FIG. 5 is a perspective view showing the structure, and FIG. 5 is a sectional view showing the structure of a semiconductor laser manufactured by another conventional method. 31...Graphite boat 32...
......Melt holder 33...Slide plate 35...Substrate 36.37.38.39...Solution reservoir 40.41.4
2.43...Solution material 45...Liquid sealing material

Claims (1)

[Claims] A solution material made of a predetermined material contained in a plurality of solution reservoirs of a solution holder is melted, and a substrate is sequentially brought into contact with the melted solution material to form a predetermined compound semiconductor crystal on the substrate. In the liquid phase crystal growth method of sequentially laminating layers, the crystal growth is performed by causing the solution material to contain a liquid sealing material that covers the surface of the solution material and blocks vapor generated from the solution material when the solution material is melted. Liquid phase crystal growth method.