Photoluminescence Studies on Semi-Insulating In-Doped Dislocation-Free GaAs Grown by LEC Method

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Abstract
Photoluminescence studies were performed at 4.2 K for In-doped dislocation-free GaAs. Large inhomogeneity of carbon-related PL intensity was observed along axial growth direction in an as-grown ingot. It was revealed that the PL intensity was strongly affected by thermal history to which it was subjected during crystal growth. After wafer or ingot annealing, the PL intensity increased and the inhomogeneity was imporved significantly. These observations cannot be explained only by concentrations of carbon and deep donor EL2. Consequently, the PL intensity depends mainly on nonradiative recombination centers and less on EL2.