Persistent photoconductivity in low-energy argon ion-bombarded semi-insulating gaAs

Time-dependent phototransport measurements are presented for low-energy argon ion-bombarded semi-insulating liquid-encapsulated Czochralski GaAs. Distinct changes caused by ion beam etching were persistent photoconductivity and an increase in photosensitivity. The time dependence of photoconductivity indicated direct participation of the EL2 center. An ion beam induced and optically generated metastable defect state is suggested in the near-surface disordered region to describe the observed phenomena.