DEFECT PROCESSES CAUSING FREE-CARRIER VARIATIONS AROUND DISLOCATIONS IN N-TYPE DOPED GAAS

Photoetching and Raman microprobe are used for the investigation of el ectrical 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 dislocat ion-induced variations of the carrier concentration for both materials , identifying defect atmospheres of dislocations as areas with a reduc ed dopant concentration on the As-sublattice. The reduction may be due to an interstitial-type diffusion of these dopants and their subseque nt gettering at the dislocation. (C) 1997 Elsevier Science S.A.