JPS5841798A - Liquid-phase epitaxial crystal growth - Google Patents

Abstract

PURPOSE:To enable the control of the distribution of a component in an epitaxial growth layer during the growing stage, by preparing a solution for replenishing a solute separately from the solution for growth, and adding the replenishing solution to the growth solution by the external operation in the course of the crystal growth. CONSTITUTION:The compound semiconductor substrate 1 is held with the holder 2, and the solution 3 for crystal growth and the solution 5 for replenishing the solute are contained in the vessel 4 and the cavity 6, respectively. When the temperature gradients of the substrate 1 and of the space above it are adjusted to the preset conditions, and the vessel 4 is lifted with the operation rod 7, the solution 3 flows down through the solution outlet hole 8 at the bottom of the vessel 4 and covers the substrate 1. The jig shown in the figure is cooled as a whole keeping the above temperature distribution to start the crystal growth. In the course of the crystal growth, the vessel is further lifted upward to add the solution 5 through the tunnel 9 to the solution 3. The desired amount of the solute can be replenished to the solution 3 at an arbitrary time by this method.

Description

[Detailed description of the invention] The major invention is liquid phase epitaxial growth method, compound half △ The present invention relates to a liquid phase epitaxial growth method for conductors.

Taking liquid phase epitaxy of G a 1-XMXAB as an example,
The shortcomings of the prior art will be explained. However, 0<X<1.

In the growth of Ga1XAIA'8, the effective segregation coefficient of M is 1.
Due to the larger size, the concentration in the growth solution decreases rapidly with growth, and as a result, the M mixed crystal ratio of the epitaxially grown layer also decreases rapidly. For this reason, it has the same drawbacks and inconveniences as the conventional wide one.

(1) A uniform M mixed crystal ratio cannot be obtained in the thickness direction of the grown layer. (In the case of cooling method) (2) In order to obtain the desired M mixed crystal ratio on the surface of the growth layer, it is necessary to set the M mixed crystal ratio at the start of growth to be high.

For this reason, there is usually a large difference in lattice constant from GaAs used for the substrate, and there are limits to the mixed crystal ratio and thickness, such as wafer curvature or cracking when grown several hundred micrometers thick.

(3) There is a temperature difference method as an epitaxial growth method that does not involve a decrease in the A# mixed crystal ratio, but this method requires floating a Ga1-xuxAs polycrystal above the growth solution. Furthermore, polycrystals of Ga1-XMXAB are difficult to obtain and the growth rate is extremely slow, making them unsuitable for industrial purposes.

An object of the present invention is to eliminate the drawbacks of the conventional techniques described above and to provide a novel liquid phase epitaxial growth layer in which the component distribution in the growth direction of the epitaxial growth layer can be controlled during the growth process.

The gist of the present invention is to prepare a solute replenishment solution separately from a growth solution, and to mix the solute replenishment solution into the growth solution by external operation during the growth process, so that a desired amount of solute can be delivered at a desired time. The purpose is to replenish the growth solution and control the component distribution of the epitaxial epitaxial layer.

Although graphite is generally used in compound semiconductor epitaxy equipment, other materials such as quartz, boron nitride, etc., or a combination thereof may also be used.

Various methods of mixing the solute replenishment solution into the growth solution can be considered, and a method suitable for the target shrimp and shrimp and the structure of the apparatus to be used can be selected. In short, any structure and method may be used as long as the solution can be mixed during growth.

In this respect, it is clearly distinguished from the multilayer slide growth method in which growth is temporarily stopped and an epitaxial layer of a different composition is grown again.

As a means of replenishing solute to the growth solution, part or all of the replenishment solution may be mixed with the growth solution, or the solutions may be simply brought into contact and the solute is supplied to the epitaxial growth interface by diffusion. Also good.

Two or more types of solutes may be supplemented.

There may be a plurality of solute replenishment solutions and their storage parts,
In this case, different solutes can be supplied separately, further expanding the range of applications.

The Ga1-XAtXAθ epitaxial growth on a G, aAs substrate according to the present invention will be specifically explained below with reference to Examples.

[Example 1] Figure 1 shows a graphite epitaxy jig used in the implementation of the present invention.
substrate holder 2 that accommodates Ga 30 t%Ga
A container 4 for storing a growth solution 3 made of As 3.3f and A15011v, a part 6 for storing a solute replenishment solution 5 made of Ga10r and M80, and an operating rod 7 for operating the container 4 from the outside: r: ing. After setting the substrate at 950°C and the temperature above the substrate at a high temperature of 20°C/CrIL in the vertical direction, and reaching these temperature conditions,
The container 4 is moved upward seven times using the operating rod 7 as shown in FIG. As a result, the growth solution 3 flows down from the solution inflow hole 8 provided at the bottom of the container 4 and covers the substrate 1 . Here, the entire jig is cooled at a rate of 0.1° C./M while maintaining the above temperature gradient, and growth is started. After 10 minutes, transfer container 4 to the third
Further move upward 311III+ as shown in the figure. As a result, the solute replenishment solution 5 is mixed into the container 4 via the tunnel 9. The mixture was further cooled in this state for 5 hours.

Gal-XAffi XA obtained by such growth
The thickness of the S growth layer was approximately 450 μm.

The Ga I The measurement measures the energy gap using photoluminescence.
This was done by converting this into an M mixed crystal ratio. Figure 4 is M
The distribution of the mixed crystal ratio is shown. The curve 1° shows the distribution of the mixed crystal ratio of the grown layer produced according to the present invention, and the uniformity of the M mixed crystal ratio is maintained throughout the growth. Curve 11 is obtained by the conventional epitaxial growth method, and the M mixed crystal ratio of the grown layer decreases rapidly.

In the conventional method, the M mixed crystal ratio at a thickness of 400 μm is set to 0.3.
In order to achieve this, the mixed crystal ratio at the start of growth must be increased to about 0.5, which increases the difference in lattice constant from the GaAS substrate, leading to cracking of the wafer.

In the present invention, M is replenished from the replenishment solution with a high M concentration into the growth solution by diffusion, and the mixed crystal ratio distribution of the growth layer indicates that M is replenished in an amount corresponding to the decrease in M. be understood from.゛The present invention provides iGa1-XMX
AS grown layers have been extremely useful as light-transmitting layers in light-emitting diodes.

[Example 2] By replenishing doping impurities, a GaAs epitaxial growth layer having a carrier concentration distribution shown in FIG. 5 can be obtained on a GaAs substrate. The jig was almost the same as that used in Example 1, but the diameter of the tunnel 9 was expanded to 5 m. Container 4 contains Ga20f, GaAs5f, T
Store e2.511v and add GIQ? to the replenishment solution section 6. ,
GaA's 6.8 t and Te 5.5"lF were stored. The temperature conditions were exactly the same as in Example 1. The operation of moving the container 4 for solute replenishment was carried out 20 minutes after the start of growth. The growth was then stopped for 10 minutes.As a result, a GaAs epitaxial growth layer with the carrier concentration distribution shown in Figure 5 was obtained.This was a very effective means for continuously growing n10 layers. .

As explained above, the most significant effect of the present invention is that by replenishing the desired solute at any time during epitaxial growth, epitaxial growth with a desired mixed crystal composition distribution or impurity concentration can be obtained in the thickness direction. be. The most effective application example is Ga 1-
Several hundred μm in thick film epitaxy of N x A 8
It is possible to obtain a uniformly grown layer with M mixed crystals in a short time and with good reproducibility.

[Brief explanation of drawings]

1, 2, and 3 are explanatory diagrams showing each process in an embodiment of the growth method of the present invention, FIG. 4 is a diagram showing the distribution of the M mixed crystal ratio, and FIG. is a diagram showing carrier concentration distribution. 1: Substrate, 2: Substrate holder, 3: Growth solution, 4: Container for storing the growth solution, 5: Solute replenishment solution, 6: Part for storing the solute replenishment solution, 7: Operation rod, 8: Solution inflow hole, 9 two tunnels, 10: M mixed crystal ratio distribution obtained by the present invention, 11: M mixed crystal ratio distribution obtained conventionally.

Claims (1)

[Claims] 1. A first step of bringing an epitaxial layer growth solution into contact with a compound semiconductor substrate crystal, and a second step of mixing a solute replenishment solution into the epitaxial layer growth solution during the epitaxial layer growth process. A liquid phase epitaxial growth method characterized by: 2. Store the epitaxial layer growth solution in a container that can be raised and lowered, arrange the tunnel and the solute replenishment solution so that when the container is raised, the solute replenishment solution mixes with the epitaxial layer growth solution, and perform the second step. A liquid phase epitaxial growth method, characterized in that the container is raised.