Mechanism responsible for the semi-insulating properties of low-temperature-grown GaAs

The mechanism responsible for the semi-insulating properties of low-temperature-grown GaAs is investigated by determining the concentration of arsenic antisite (AsGa)-related defects in the material. The concentrations of the defects in neutral and positively charged states, As0Ga and As+Ga, are determined by near-infrared absorption and magnetic circular dichroism of absorption, respectively. Materials grown and annealed at different temperatures are investigated. We find that the defects are abundant in all samples studied, with the concentration of As0Ga higher than that of As+Ga defects. The results indicate that the defects can account for the pinning of the Fermi energy and consequently also the semi-insulating properties of the material.