JPS63119227A - Liquid growth method - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of the solute concentration of the bottom of a growth solution, and to improve the composition of an extremely thin film layer and the reproducibility and uniformity of film thickness by making the area of an upper hole larger than that of a lower hole in the shape of a solution reservoir for sliding growth and forming a slot in a direction perpendicular to the direction of sliding to the lower section of the solution reservoir in extremely thin-film epitaxial growth through a liquid growth method. CONSTITUTION:When an InGaAsP/InP quantum well type epitaxial layer is shaped, upper holes are made larger than lower holes in the shape of solution reservoirs 2', 3', 4' for barrier layer solutions 2, 4 and a well layer solution 3, and lower holes 8, 9, 10 are each formed to said solution reservoirs 2', 3', 4'. The lower holes 8, 9, 10 are formed to a striped shape in the direction rectangular to the direction 11 of sliding. Since loading density applied to the bottoms of growth solutions is increased and the length of the direction 11 of sliding of the bottoms is shortened in the growth solutions received to the solution reservoirs having such a shape, the convection and vibrations and fluctuation of the solutions of the solution bottoms generated at a time when the slider 11 is slid are inhibited. Accordingly, the variation of the composition of solute concentration in the solutions is suppressed, thus allowing growth having reproducibility and uniformity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid phase growth method used for forming ultra-thin epitaxial layers.

Conventional technology Conventionally, the molecular beam epitaxial method, the organic 2' metal vapor phase epitaxy method, etc. have been mainly used to form ultra-thin epitaxial layers such as quantum well type layers, and the liquid phase epitaxy method has a faster growth rate. Because it is extremely difficult to control the thickness of an extremely thin film layer (600 people), it has rarely been implemented.

However, it is widely known that the liquid phase growth method is currently the most superior in terms of simplicity of growth equipment, price, and crystallinity of the growth layer itself, and it is possible to form ultrathin film layers with good controllability. Formation is extremely important in practice.

Regarding the formation of an ultra-thin epitaxial layer by the liquid phase growth method, Japanese Patent Application No. 59-216654 (Japanese Unexamined Patent Publication No. 61-198)
-97189). The outline of this patent application will be briefly explained below.

When forming an ultra-thin epitaxial layer using a liquid phase growth method, the growth rate is fast, so it is necessary to grow in a very short growth time, usually one second or less. Therefore, the sum (11+13) of the time t1 for sliding the substrate to completely contact with the solution and the time t3 for sliding the substrate and completely wiping off the solution is the sum (11+13) of If the holding time is about the same as or longer than t23 b/, the growth time cannot be defined and the thickness of the grown layer cannot be controlled. Therefore, in the above patent application, a method of ``sliding growth'' is adopted in which growth is performed while the substrate is sliding at a constant speed without stopping while it is brought into contact with the solution.
, where the growth time tg is defined by the ratio L/'v of the length L of the solution reservoir and the sliding speed V.

A schematic diagram of the apparatus system used in the conventional patent application is shown in FIG. 1 is a substrate, 2, 3.4 is a growth solution, 6 is a slider that accommodates the slidable substrate, 6 is a solution holder that accommodates the growth solution, and 7 is a boat stand. However, when creating a multiple quantum well structure, the growth solution 2, 4
If 3 is a barrier layer solution and 3 is a well layer solution for an extremely thin film, the substrate 1 will be grown by sliding back and forth between barrier layer solutions 2 and 4, but at this time, the forbidden band width of the well layer will be small. As a result, the half-width of the spontaneously emitted light of the multi-quantum well layer widens, and a phenomenon of compositional fluctuation occurs3.The reason for this is that when the substrate 1 is slid, the Since the bottom surface is in contact with the slider 5, the well layer solution 3
This is thought to be because the bottom surface of the solution is shaken, causing convection in the solute in the solution, causing fluctuations in the solute concentration. Because the growth occurs while the substrate is being moved, wetting between the substrate surface and the growth solution is poor, resulting in non-uniform film thickness.

Problems to be Solved by the Invention As mentioned above, in the conventional method, ultra-thin films by liquid phase growth,
In particular, when a multi-quantum well structure is fabricated, the composition of each well layer is slightly different, and the film thickness is non-uniform. The present invention provides a method for making the composition of each well layer uniform and forming a well layer with good uniformity in thickness.

Means for Solving the Problems In order to solve the above problems, growth is performed using the sliding growth method described above, and the shape of the solution reservoir that stores the growth solution is changed so that the area of the upper hole is larger than the area of the lower hole. By forming the pilot holes into a striped structure, it is possible to prevent fluctuations in the solute concentration at the bottom of the growth solution, thereby improving the reproducibility and uniformity of the composition and thickness of the ultra-thin film layer. It is something.

The effects based on the means described in Effect 5-- are as follows. That is, by making the shape of the solution reservoir as described above, the weight of the solution is concentrated toward the bottom of the growth solution, and since the width of the groove at the bottom is narrow, the bottom of the solution is not easily moved by the sliding of the slider. On the other hand, the flow is considerably relaxed, so that the solute concentration at the bottom of the solution hardly changes, and the uniformity of the composition and film thickness can be improved.

Example 3 An example of the present invention will be described below with reference to FIG.
Note that in FIG. 1, the same components as those in FIG. 4 are designated by the same reference numerals, and explanations thereof will be omitted. In order to simplify and make the explanation more concrete, an example of forming an InGaAsP/InP well type epitaxial layer will be described below.

Here, the difference between the boat structure in this example and the conventional one is that, as can be seen by comparing FIG. 1 and FIG. Regarding the shape of the reservoirs 2', 3', and 4', the hole C11 is larger than the pilot hole, and the pilot holes 8, 9, 10 of the solution 6', /' reservoirs 2', 3', and 4' are larger than the pilot hole. are provided for each. Here, the pilot holes 8, 9.10
are formed in a stripe shape in a direction perpendicular to the sliding direction 10. In a growth solution stored in a solution reservoir having such a shape, the weight density applied to the bottom of the solution increases, and the length of the bottom in the sliding direction 11 is small, so that the solution at the bottom of the solution occurs when the slider 11 slides. convection and vibration fluctuations are suppressed. Therefore, fluctuations in the composition of the solute concentration in the solution are suppressed, making it possible to achieve reproducible and uniform growth.

The growth conditions were a solution temperature of 620'C for 1 hour, and a cooling rate of o.
, the temperature was lowered at a rate of 5°C/min, and growth was performed in a hydrogen gas atmosphere at 590°C. In Fig. 1a, the growth was started by first sliding the slider 5 at a constant speed vB.
The InP substrate 1 is passed under the groove 8 to grow an InP barrier layer, and then the slider 5 is slid at a constant speed Vw to pass the InP substrate 1 under the groove 9 to grow an InP barrier layer.
A P well layer is grown, and finally, as shown in Figure 1, the slider 5 is moved at a constant speed VB to pass the InP substrate 1 under the groove 10 to grow one layer of the InP substrate. The single quantum well structure is completed.

In the case of a multi-quantum well type structure, it can be manufactured by sliding the slider 6 back and forth following the above-mentioned process. Regarding the dimensions of the solution reservoirs 2/, 3/, and 4/, when the length of the substrate 1 in the sliding direction is L, the length of the upper hole of the solution reservoirs 2', 3', and 4' in the sliding direction is The lengths of the grooves 8, 9, and 10 in the sliding direction are L/N, respectively.
child. However, since the growth rate differs depending on the composition of the growth solution, from the viewpoint of controllability of the film thickness, it is preferable to arbitrarily change the value of N and grow under optimal conditions. Although it is not shown in Figure 1, an even greater effect can be expected if a weight is added on top of the growth solution.

Next, another embodiment of the present invention will be described using FIG. 2. The difference between this example and the previous example is +1, in that not only grooves 8, 9, 10 were similarly provided in the solution reservoirs 2, 3, 4, but also slopes 11, 12, 13 were added. , this increases the weighted density of the solution in the pilot holes 8, 9, and 10,
Fluctuations in the solute concentration at the bottom of the growth solution that occur when the slider 5 slides are well suppressed. Therefore, improved controllability of composition and film thickness can be expected for ultra-thin film growth.

Next, still another embodiment of the present invention will be described with reference to FIG. The differences between this embodiment and the first embodiment are as follows:
Similarly, grooves 14.degree. 15.16 are provided in the solution reservoirs 2, 3.4, but the shape of the grooves 14, 15.16 is such that the side surfaces thereof are inclined as shown in FIG. This allows groove 1
The weighted density of the solution in 4, 15.16 is increased, and fluctuations in the solute concentration at the bottom of the growth solution that occur when the slider 6 slides are further suppressed, making it possible to control the composition and film thickness for ultra-thin film growth. We can expect improvement.

Effects of the Invention As described above, according to the present invention, in ultrathin film epitaxial growth by liquid phase growth, when growing using sliding growth, the shape of the solution reservoir is such that the upper hole area is larger than the lower hole area, By providing a slot in the lower part of the solution reservoir in a direction perpendicular to the sliding direction, fluctuations in the solute concentration at the bottom of the Boehno liquid that occur when the slider slides can be suppressed and the composition can be reduced.

Ultra-thin film layers with uniform thickness can be produced with good reproducibility.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view of a growth boat illustrating a liquid phase growth method in an embodiment of the present invention, and FIG. 2 is a sectional view of a growth boat in a second embodiment of the present invention. Figure 3 shows the third embodiment of the present invention.
FIG. 4 is a sectional view of a growth boat for explaining the conventional liquid phase growth method. 1...Substrate, 2,4...Barrier layer solution, 3.River...Well layer solution, 8,9.10...Prepared hole, 11, 12゜13 ... Sloped side wall of solution reservoir, 14, 15.16 ... Slanted side wall of groove.

Claims (1)

[Claims] Using a growth boat that has a substrate holder for storing a substrate and a solution holder for storing a solution, and in which the substrate holder and the solution holder are movable relative to each other, the substrate holder and the solution holder are relatively slidable. When performing ultrathin film epitaxial growth by growing in a sliding state without stopping, the area of the upper hole of the solution reservoir provided in the solution holder is made larger than the area of the pilot hole, and the shape of the pilot hole is striped. A liquid phase growth method characterized by: