POINT-DEFECT STRUCTURES IN GALLIUM-ARSENIDE STUDIED BY POSITRON SPECTROSCOPIES

Positron spectroscopies have been used to examine the point defect structure of gallium arsenide. Experiments have been performed to investigate the properties of native defects in as-grown GaAs. Furthermore, the defect production during electron irradiation, hydrogen implantation and plastic deformation of GaAs have been studied by positron techniques. New information is obtained especially on the properties of vacancy defects. In as-grown GaAs, the ionization levels of arsenic vacancies are determined. In semi-insulating GaAs, the metastable state of the EL2 defect is shown to contain a monovacancy. The introduction of vacancies and antisite defects to the gallium sublattice is observed in electron irradiation of GaAs. In deformed GaAs, the simultaneous formation of vacancies, antisites and vacancy complexes is detected. Finally, the depth distributions of vacancies are determined after hydrogen implantation in semi-insulating GaAs, and the recovery of the implantation damage during isochronal annealing is investigated.