Device-relevant point defects in GaAs and InP

Positron annihilation is used to determine the vacancy ionization levels and the atomic structure of acceptors, vacancy-type or ion-type, in GaAs and InP materials. Positron annihilation yields information on the size of the vacancy open volume via the annihilation lifetime in the vacancy τV, on its charge state via the positron trapping coefficient μV(T) and the concentration CV via the positron trapping rate KV = μVCV. It is shown that V(As) and V(Ga) vacancies play a role as compensating centers in semi-insulating (SI) and n-type GaAs. V(As) vacancies absorb near-band edge light and interact with holes or electrons depending on their charge state V(As)+, V(As)0 or V(As)−. The conversion EL2 to EL2* generates metastable vacancies which are part of the EL2* structure.