Positron mobility and interface defect studies in semi-insulating GaAs using the lifetime technique

Abstract

Measurements of positron mobility in semi-insulating GaAs using the lifetime technique have been carried out with applied electric fields in the samples directed towards and away from the positron injecting contact. Micro-void defects at the Au/GaAs interface having a characteristic of lifetime of 395ps have been observed. The large increasing trend in the intensity of the interface lifetime component as the field is directed towards the contact is well explained by a two value electric field model and the data is found to be consistent with a positron mobility value of 60 cm2V-1s-1. We point out that such a large fraction of positrons annihilating from the metal-semiconductor interface allows a study of interface positron states to be made without resorting to the use of a positron beam.