Defect processes causing free carrier variations around dislocations in n-type doped GaAs

Photoetching and Raman microprobe are used for the investigation of electrical inhomogeneities in the vicinity of grown-in dislocations in n-type GaAs doped with Si and Te, respectively. In GaAs:Si, an increase of the free electron concentration is detected, whereas the reverse, and with a more pronounced effect, is seen in GaAs:Te. A microscopical mechanism is proposed which allows the interpretation of the dislocation-induced variations of the carrier concentration for both materials, identifying defect atmospheres of dislocations as areas with a reduced dopant concentration on the As-sublattice. The reduction may be due to an interstitial-type diffusion of these dopants and their subsequent gettering at the dislocation.