JPS643051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for liquid phase growth of multicomponent semiconductor crystals, particularly to an improvement in a method for forming a plurality of growth layers.

Semiconductor laser devices are usually manufactured by a multilayer epitaxial growth method from a liquid phase. This epitaxial growth method is already well known, but the first method will be described below.
This will be briefly explained using figures.

In FIG. 1, A is a plurality of liquid reservoirs 1, 2, 3.
B is a carbon boat having a substrate holder also made of carbon. A single crystal substrate 4 of a multi-component semiconductor such as lead telluride (PbTe) and a dummy wafer 5 are placed and held on the B surface of the substrate holding table. The single crystal substrate 4 serves as a support for the active portion of the semiconductor laser device, and the dummy wafer is used to remove unnecessary impurities accumulated in the lower layer of the semiconductor solution. In other words, carbon boat A
When the liquid phase is moved, a solution of a multi-component semiconductor, such as a ternary semiconductor containing lead, housed in the liquid reservoirs 1, 2, and 3 comes into contact with the surface of the carbon substrate holder B, and unnecessary impurities are mixed into the liquid phase. easy. Therefore, before bringing the solution 7 into contact with the single crystal substrate 4, crystals containing unnecessary impurities are precipitated from the bottom of the liquid phase on the dummy wafer 5, thereby cleaning the liquid phase.

Furthermore, in this type of liquid phase growth process, before the growth starts, the temperature of a heating furnace (not shown) is raised at the boat position shown in FIG. Dissolve. This melting process is commonly referred to as melt back. This step removes a thin layer on the surface of the substrate, leaving the surface with a good surface suitable for epitaxial growth. Therefore, the temperature of the furnace is lowered and the solution 6 in the liquid reservoir 1 is grown as a single crystal on the surface of the substrate 4.

During the manufacturing process of the semiconductor laser device described above, the substrate 4
The first liquid phase that is brought into contact with the substrate 4 is the liquid phase 6 for forming a buffer layer.After this, the boat A is shifted in the direction of arrow A, and the active layer growth solution 7 is brought into contact with the substrate 4 to form a growth layer that will become an active layer. form. Since the emission wavelength of the completed semiconductor laser is determined by the composition of the active layer, the composition of the active layer must be strictly defined in order to obtain output light precisely matching the desired wavelength.

However, according to the conventional epitaxial growth method described above, the dummy wafer 5 dissolves to some extent in the active layer growth solution 7 during meltback, and as a result, the composition of the active layer growth solution 7 fluctuates. There was an inconvenience that the composition of the grown active layer differed from the originally designed value.

The present invention solves the above-mentioned problem, which is caused by using a boat having an extra liquid reservoir than the required number of growth layers, which causes dummy wafer components to dissolve into the liquid phase during meltback. The purpose of the present invention is to provide a new method for liquid phase growth of multicomponent semiconductor crystals that makes it possible to prevent fluctuations in the liquid phase composition.

An embodiment of the liquid phase growth method according to the present invention will be described in detail below with reference to the drawings. Note that in the following figures, the same parts as in FIG. 1 are given the same reference numerals.

FIG. 2 shows the state during meltback in the liquid phase growth method according to the present invention, and in this example, lead-tin-tellurium (Pb ₁ -χ Snχ Te) is grown from the liquid phase.

Boat A' used in this embodiment has one more liquid reservoir than boat A in FIG.
This extra liquid reservoir 9 contains a solution 10 having the same composition as the buffer layer growth solution 6. Since the extra liquid reservoir 9 is located in front of the liquid reservoir 1 containing the buffer layer growth solution 6, its contents 10 reach the surface of the substrate 4 before the contents 6 of the liquid reservoir 1. Contact. Therefore, as shown in FIG.
Meltback is performed by raising the furnace temperature while the two are in contact with each other. At this time, since the liquid reservoir 2 for growing the active layer is separated from the dummy wafer 5, there is no possibility that the dummy wafer 5 will dissolve in the solution 7.

When the melt-back process is completed in this way, the boat A is moved in the direction of arrow A so that the buffer layer growth solution 6 comes into contact with the surface of the substrate 4 as shown in FIG. 3, and the furnace temperature is lowered. A growth layer, which will become a buffer layer, is then grown on the new surface of the substrate 4. In addition, in the state shown in FIG. 3, the active layer growth solution 7
is in contact with the dummy wafer 5, but since the furnace temperature has decreased, the dummy wafer does not melt, that is, the dummy wafer does not melt back into the solution 7. Therefore, there is no change in the composition of solution 7, but
Regarding the cleaning of the liquid phase by the dummy wafer 5, there is no difference from the case shown in FIG.

Once the growth layer that will become the buffer layer has been formed as described above, the rest is done by boating as in the conventional method.
Move the boat A' in the direction of arrow A to bring the solution 7 for active layer growth into contact with the upper surface of the substrate 4 to form a growth layer that will become the active layer, as shown in Figure 4, and then move the boat A' further. The liquid phase epitaxial growth process is then completed by laminating and forming a growth layer that will become the top layer on the substrate 4 from the top layer growth solution 8. According to this process, since the semiconductor material does not dissolve into the liquid phase for active layer growth, it is possible to form an active layer with exactly the same composition as the solution immediately after preparation, and therefore the active layer can be used as a laser output. It is possible to extract light at a wavelength that exactly corresponds to the theoretical composition of . According to experiments conducted by the present inventors, semiconductor lasers manufactured using the conventional growth method had an error of up to ±0.5 μm compared to the design value in the emission wavelength, but the growth method of the present invention In this case, the above error could be kept within ±0.2 μm.

Although it is ideal to use a dummy wafer of the same quality as the active layer, it is acceptable if there is a slight difference in composition. It may also be polycrystalline.

The embodiment described above was for growing Pb ₁ -χSNχTe, but if a liquid phase epitaxial method using a dummy wafer and involving meltback is used, a gallium arsenide (GaAs) based binary or ternary semiconductor, The method of the present invention can also be effectively applied to other chalcogen-based multicomponent semiconductors, such as mercury-cadmium-tellurium (Hg ₁ -χCdχTe).

According to the liquid phase growth method according to the present invention, it is possible to prevent compositional fluctuations in the liquid phase during meltback, so there is an excellent advantage that an epitaxial growth layer having a composition that precisely matches the planned composition can be obtained. . Therefore, it is extremely advantageous especially when applied to the manufacture of semiconductor infrared laser elements used as light sources of atmospheric analysis devices, which require precisely adjusting the wavelength of output light to a desired value.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of an apparatus used in the conventional liquid phase growth method, and FIGS. 2 to 4 are cross-sectional views sequentially showing an example of the manufacturing process of a semiconductor laser device to which the liquid phase growth method of the present invention is applied. It is a diagram. A, A: Boat, B: Substrate holding stand, 1, 2,
3: Liquid reservoir, 6: Buffer layer growth solution, 7: Active layer growth solution, 8: Top layer growth solution, 9:
Liquid reservoir, 10: Solution for melt bag.

Claims (1)

[Claims] 1. A method for successively growing a buffer layer, an active layer, and a top layer in this order on a crystal growth substrate by a sliding liquid phase epitaxial growth method, comprising: a substrate holder for holding a crystal growth substrate and a dummy wafer; A platform and a boat having four liquid reservoirs each containing a multi-component semiconductor liquid phase are stacked one on top of the other, and the buffer layer growth solution contained in the first and second liquid reservoirs is placed one above the other. The surfaces of the substrate and dummy wafer are brought into contact with each other to dissolve the surface layer portions of the substrate and dummy wafer in the respective solutions, and then the boat and the substrate holder are moved relatively to each other and placed in a second liquid reservoir in the boat. The prepared buffer layer growth solution is brought into contact with the substrate, and the active layer growth solution in the third reservoir is brought into contact with the dummy wafer, and multi-component semiconductor crystals are grown from each solution onto the surfaces of the substrate and dummy wafer while lowering the solution temperature. After that, the boat is moved relative to the substrate holder and the active layer growth solution in the third reservoir is applied to the substrate surface.
The top layer solution in the fourth reservoir is brought into contact with the surface of the dummy wafer, and multi-component semiconductor crystals are precipitated and grown from each solution, and then the boat is moved relative to the substrate holder to grow the top layer in the fourth reservoir. A liquid phase growth method for multi-component semiconductor crystals, characterized in that multi-component semiconductor crystals are precipitated and grown by bringing a solution into contact with a substrate surface.