SEMI-INSULATING GALLIUM ARSENIDE SINGLE CRYSTAL HAVING LOW DISLOCATION DENSITY

摘要

PURPOSE:To obtain the above single crystal having decreased dislocation density by impurity hardening effect, by adding Cr and Al in the production of a GaAs single crystal by a boat method or a liquid encapsulated pulling-up method. CONSTITUTION:A GaAs single crystal is produced by a boat method or a liquid encapsu lated pulling-up method. In the case of, e.g., a boat method, a quartz boat containing a seed crystal and a raw material Ga together with Cr and 1017-1020cm-3 of Al is placed at one end of a reaction tube made of a quartz glass. After placing As at the other end, the reaction tube is sealed. The tube is inserted into e.g. a tandem electric furnace, etc., and the temperature of the tube is maintained to =1,200 deg.C at the boat-side and to about 600 deg.C at the As-side. After the completion of the GaAs synthesis reaction, the boat-side temperature is further raised while keeping the As-side temperature unchanged and the temperature in the furnace is controlled in such a manner as to keep the seeding part at the melting point of GaAs (1,238 deg.C) and increase the temperature toward the side of the boat main body at a temperature gradient of about 1 deg.C/cm. After melting a part of the seed crystal, the reaction tube is cooled at a rate of 1 deg.C/hr while keeping the above temperature gradient until the whole molten liquid is solidified to obtain the above single crystal.