Bulk GaAs grown by the Bridgman technique changes its electronic properties in response to heat treatment. These changes were studied by deep level transient spectroscopy, photoluminescence, and Hall effect measurements. We report the dependence of the conductivity changes on starting material composition, annealing temperature, and annealing duration. The changes are related to the stability of a shallow acceptor which is present in concentrations ge;1016cmminus;3and reflect the equilibration of native defects introduced during the crystal growth process. The implication of this study is that ashyphen;grown GaAs is a metastable material with its ultimate electrical properties being determined by process conditions.
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