ABSTRACT
During the process in growing a GaAs single crystal ingot with the liquid encapsulated Czochralski (LEC) method, the thermal environment is varied at the different growth portions; that is, the shoulder portion where the diameter of crystalline ingot is increased from seed, the middle portion where the crystalline ingot is continuously grown, and the tail portion where the crystalline ingot is released from melt. Therefore, thermal stress is varied from portion to portion of the crystalline ingot. During the thermal annealing process carried out after the crystal growth process, the thermal stress is also changed by the ingot-supporting method as well as by the thermal environment. This thermal stress is understood to be the main cause of slip dislocation generation and hence to be the origin of residual stress or strain in the crystalline ingot. If we can measure such residual stress or strain, we may evaluate and optimise the thermal environment during the crystal growth and thermal annealing processes.
