COMPOUND SEMICONDUCTOR SINGLE CRYSTAL OF LOW DISLOCATION DENSITY, ITS PRODUCTION AND APPARATUS FOR PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a single crystal substrate capable of emitting a visible light diode with a high luminance by regulating a part of a surface area at a specific ratio or above based on the whole to a dislocation density of a specified value or below. SOLUTION: This compound semiconductor single crystal such as GaP has <=500/cm<2> dislocation density in a part of surface area of >=90% based on the whole, <=5×10<16> /cm<3> oxygen concentration and <=5×10<16> /cm<3> boron concentration. The temperature gradient in the growth axial direction applied to the growth system is regulated so as to provide a small one of <=7 deg.C/cm in the upper region and a large one in the lower region of 2-4 times the temperature gradient in the upper region in a step for growing the semiconductor single crystal from the lower to the upper sides according to a vertical Bridgman method or a vertical temperature gradient method. Thereby, the solid-liquid interfacial form is upward convex in the lower region and is horizontal in the upper region. A boundary part changing the temperature gradient is located near a diameter increasing part of the growth system to advance the solidification. Thereby, the single crystal, hardly forming a twin or a polycrystal and having a low dislocation density is obtained.