Mobility in epitaxial GaAs under 1-MeV electron irradiation

Vapor-grown epitaxial layers of undoped n-type GaAs show an anomalous large decrease in apparent mobility upon irradiation with a small dose of 1-MeV electrons. As the dose is increased, the samples become p type. The results cannot be accounted for by a uniform distribution of radiation-induced point defects. It is proposed that spatial inhomogeneity is induced by the irradiation. A possible mechanism is the ionization-induced migration of deep donors to a network of dislocations in the layer. This migration can be reversed by annealing.