JP2765120B2 - Liquid phase epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for epitaxially growing an AlGaAs mixed crystal semiconductor crystal.

(B) Conventional technology Ultra-bright red light emitting diodes and ultra-high output infrared light emitting diodes are AlGaAs thick film crystals (50 to 50 mm) that are transparent to emitted light in order to improve light extraction efficiency.
100 μm), and p-type and n-type AlGaAs layers and G
forming an aAs layer, or adding p-type, n-type
It is manufactured by diffusing a shaped dopant. This AlGaAs thick film crystal is generally obtained by growing it on a GaAs substrate using a liquid phase epitaxial growth method.

(C) Problems to be Solved by the Invention However, if there are many defects called stacking faults in an AlGaAs thick film crystal, a light emitting diode manufactured using this thick film crystal will deteriorate when subjected to long-term energization. And the light emission output gradually decreases. FIG. 2 shows the light emission output after 48 hours of energization at 150 mA when the initial light emission output is set to 100%. From this, when the number of stacking faults becomes 10 ² cm ⁻² or less, the deterioration rate of the light emission output becomes considerably small. You can see that. However, it has been difficult to obtain AlGaAs thick-film crystals with a small number of stacking faults in the past, and the number of stacking faults is usually 10 ³ cm ^-2 to 10 ⁴ cm ^-2 , and therefore high-quality light emission with little deterioration Diode could not be obtained.

B. Configuration of the Invention (a) Means for Solving the Problems The present invention solves the above problems by providing an AlGaAs mixed crystal semiconductor crystal on a GaAs substrate by a liquid phase epitaxial growth method. Constituting Ga
It is characterized in that the concentration of Si contained in As is 1 × 10 ¹⁷ cm ⁻³ or less.

(B) Action As a cause of the occurrence of stacking faults in the semiconductor crystal obtained by the liquid phase epitaxial growth method, a foreign substance adhering to the substrate surface or mixed in a raw material for epitaxial growth is considered. Particularly, when growing an AlGaAs mixed crystal semiconductor crystal, Al is easily oxidized, and the oxide Al ₂
Since O ₃ is very stable, Al ₂ O ₃ is a nucleus for the generation of stacking faults. Therefore, when epitaxial growth of an AlGaAs mixed crystal semiconductor crystal is performed, it is important to prevent oxygen (O ₂ ) from being mixed.

On the other hand, in a GaAs substrate used for liquid phase epitaxial growth, Si contained in the GaAs constituting the GaAs substrate forms SiO ₂ which is an oxide on the substrate surface. this
SiO _{2 is} also a stable substance and remains on the substrate surface immediately before epitaxial growth without being reduced even in hydrogen (H ₂ ). However, when a growth raw material solution containing Al is introduced onto the substrate surface, this SiO ₂ is reduced to produce more stable Al ₂ O ₃ . There included
Using GaAs substrates having different Si concentrations, AlxGa (1) having a mixed crystal ratio of x = 0.2 to 0.4 and a thickness of approximately 50 to 60 μm was formed thereon.
-X) The number of stacking faults when an As thick film crystal was grown was examined. The result is shown in FIG. Si concentration stacking number of defects in the GaAs substrate as seen from FIG. 1 corresponds, S in GaAs to the number of stacking faults and 10 ² cm ^-2 or less
It can be seen that it is sufficient to set the i concentration to 1 × 10 ¹⁷ cm ⁻³ or less.

Here, the GaAs substrate used for epitaxial growth is:
Since it is removed by etching or polishing in the subsequent process of fabricating the light emitting diode, a change in the electrical characteristics due to a decrease in the carrier concentration (Si concentration) does not have any particular adverse effect.

(C) Example The content of Si formed by growing by the HB method (horizontal Bridgman method) was 2.5 × 10 ¹⁶ cm ⁻³ (this example) and 5.6 × 10
900 ° C to 800 for two types of substrates of ¹⁷ cm ^-3 (conventional example)
AlxGa (1-x) As thick film crystals were grown at a rate of 0.1 ° C./min. The thickness of the thick film result obtained for both is 70
100100 μm, and the mixed crystal ratio of Al was x = 0.2-0.4. When the number of stacking faults on the surface of these AlGaAs thick film crystals was examined, the results shown in Table 1 were obtained, and the effect of the present invention was confirmed.

Furthermore, an infrared light emitting diode was prepared using these thick film crystals, and energization was performed at 150 mA for 48 hours. In the case of the conventional example, the light emission output was greatly reduced to 75% of the initial value. It was found that the light emitting output of the substrate of 90% or more of the initial level was maintained, and a high quality light emitting diode was obtained.

C. Effect of the Invention (a) Effect of the Invention By using the present invention, it is possible to obtain an AlGaAs thick film crystal having a very small stacking fault of 10 ² cm ⁻² or less,
Therefore, a high-quality light-emitting diode with almost no deterioration in characteristics even after long-time power supply can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basis of the proposal of the present invention, and FIG. 2 is a diagram showing the number of stacking faults and the degradation characteristics of light emission output.

Claims (1)

(57) [Claims] In the case where an AlGaAs mixed crystal semiconductor crystal is grown on a GaAs substrate by a liquid phase epitaxial growth method,
The concentration of Si contained in GaAs constituting the GaAs substrate is 1 ×
A method for epitaxially growing a semiconductor single crystal, which is 10 ¹⁷ cm ⁻³ or less.