Magnetic resonance and positron annihilation of intrinsic acceptors in ITC-treated GaAs

Thermal treatment near the melting point followed by a rapid quench to room temperature in semi-insulating GaAs destroy nearly all of the EL2 defects present in the as-grown material as shown previously by DLTS measurements. Two different structure-sensitive methods, i.e. positron annihilation (PAS) and optically detected magnetic resonance (ODMR) have been used to study the defects produced by such thermal treatments. In positron annihilation a new negatively charged mono-vacancy defect with a lifetime of 273 ps has been observed in addition to negatively charged ion-type defects. Both are acceptor-like defects. We attribute the higher lifetime of the vacancy, compared to Ga vacancy-related defects observed in asgrown material to a higher open volume of this vacancy-related defect. In optically detected magnetic resonance experiments three acceptor-like defects have been observed. Two of them have been related to intrinsic defects, whereas the third was ascribed to a Cu-related defect which has been incorporated during the heating processes. We suggest that one of the acceptor-like defects is the Ga vacancy - related defect with the PAS lifetime of 273 ps.