JPS6248370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel liquid phase epitaxial growth method. An object of the present invention is to reduce the number of defects in a grown layer caused by microcrystals generated in a solution.

Liquid phase epitaxial growth is generally performed in the following manner. As shown in FIG. 1, a boat 2 containing a solution 1 containing predetermined additives and a slider 4 containing a substrate crystal 3 are arranged in a state where the solution and the substrate crystal are separated. An atmospheric gas for preventing oxidation is introduced from the outside into the liquid phase epitaxial growth system. The liquid phase epitaxial growth system is maintained at a predetermined temperature for a predetermined time in a high-purity atmospheric gas to maintain the solution in a thermal equilibrium state. Thereafter, the slider is moved while lowering the temperature at a predetermined cooling rate to bring the substrate crystal into contact with the solution. During this cooling process, there is a phenomenon in which microcrystals are generated in the solution. If epitaxial growth is continued with a solution containing these microcrystals, defects lacking crystal components will be formed in the growth layer directly under the microcrystals, or microcrystals will be incorporated into the growth layer. . Semiconductor devices made using such crystals have unfavorable electrical and optical properties.

The present invention provides a method for growing crystals that contains almost no defects caused by microcrystals in a solution.

The method of the present invention will be described below. As shown in FIG. 2, while the maximum temperature is maintained, the flow rate of the atmospheric gas is minimized to suppress evaporation of components from the solution and the substrate crystal, and the flow rate of the atmospheric gas is increased shortly before the start of growth. This atmospheric gas is an inert gas or reducing gas that is flowed to prevent the solution substrate crystals and the carbon jig that holds them from being oxidized. area will cool down faster. If epitaxial growth is performed by cooling the entire furnace in this state, the microcrystals generated in the solution will be attracted to the part of the solution in contact with the boat wall and will not affect the growing layer.

Furthermore, as shown in Figure 1, if the thickness D of the slider section is made sufficiently larger than the thickness d of the wall of the boat section, heat will be removed from the boat section by the atmospheric gas faster than the slider section. , the effect of this invention is great.

Also, if the substrate area is made smaller than the solution area,
It is possible to reduce the swelling of the growth layer around the substrate due to lateral temperature distribution.

<Preferred Embodiment> Next, as an embodiment of the present invention, a case where GaAs crystal is epitaxially grown will be described.

First, in the initial process, boat 2 containing Ga melt 1 with GaAs polycrystals and dopants added and GaAs
With the Ga melt 1 and the substrate 3 separated from each other, the slider 4 housing the substrate 3 is heated to 800°C in high-purity H ₂ gas by selecting hydrogen (H ₂ ) gas as the atmospheric gas and holding it for 3 hours. The Ga melt was saturated with As. During this time, the H ₂ gas flow rate was set to 0.1/min to suppress evaporation of components from the solution and the substrate as much as possible. In the next growth process, this H ₂ increases the gas flow rate by 0.4/
After 10 minutes, the temperature started to decrease. When the temperature dropped to 5°C, the slider was moved to bring the substrate into contact with the Ga melt and growth started. 800℃ to 10℃
Once the substrate had descended, the Ga melt was removed from the substrate to stop growth. The number of defects (holes with a diameter of 1 μm or more) caused by microcrystals observed on the growth surface was less than 10 ³ /cm ² . In addition, defects of 10 ⁵ /cm ² or more were observed on the surface of the film that was grown with the H ₂ gas flow rate unchanged at 0.1/min.

The present invention is applicable not only to the growth of a single layer but also to growth layers having a multilayer structure. For example, when a double-hetero laser is grown using the present invention, defects in the grown layers, particularly in the active layer, can be reduced. When a double-hetero laser was actually created using the present invention, its continuous oscillation life at room temperature was over 5,000 hours, whereas conventional double-hetero lasers with many defects had a lifespan of less than 500 hours. Ta.

The present invention can be applied to all other semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a boat for liquid phase growth, in which a is a sectional view seen from the side and b is a sectional view seen from the front. 1...Solution, 2...Boat part, 3...Substrate crystal, 4...Slider part, d...Thickness of wall of boat part, D...Thickness of slider part. FIG. 2a is a diagram showing the growth temperature cycle. Vertical axis: temperature; horizontal axis: time; diagonal line: time during growth. FIG. 2b is a diagram showing the gas flow cycle. Vertical axis: gas flow rate, horizontal axis: time, shaded area...
Indicates time during growth.

Claims (1)

[Claims] 1 Liquid phase epitaxy in which a high purity atmospheric gas is introduced into a liquid phase epitaxial growth system in which a growth solution and a growth substrate crystal are arranged, and a layer is grown from the solution on the substrate crystal in the atmospheric gas. In the barrel growth method, an initial step of maintaining the solution at a high temperature by setting a small flow rate of the introduced atmospheric gas, and following the initial step, increasing the flow rate,
bringing the solution into contact with the substrate crystal and lowering the temperature;
A liquid phase epitaxial growth method comprising: a growth step of obtaining an epitaxial growth layer on the substrate crystal.