Optical and electrical characteristics of GaAs implanted with high energy (70MeV) 120Sn ions

Abstract

Infra-red transmission and electrical characteristics of single crystal GaAs substrates implanted with 70 MeV 120Sn ions have been investigated after implantation and subsequent annealing treatments. The optical density αx is found to increase with implanted dose over photon energy range 0.6–1.4 eV and reaches a high saturated value for the samples implanted to a dose of 1 × 10 14 ions/cm 2. The saturation of × versus hν suggests amorphisation. Annealing of higher dose samples above 350 °C reduces the density of the radiation defects. The deep lying states seem to be annealing out faster for the annealing temperatures below 450 °C while annealing of near band edge damage occurs over the annealing temperature range of 450–600 °C. The resistance values of the high dose (1 × 10 14 ions/cm 2) samples which is initially low (≤ 1 kgW), are found to increase with annealing temperatures upto 650 °C and then decrease for higher annealing temperatures. The resistance of the samples annealed up to 450 °C is dominated by variable range hopping conduction below room temperature. For the samples annealed at temperatures higher than 450 °C, the electrical transport is dominated by hopping between the neighbouring defect sites. Above 650 °C annealing temperatures, the defect states are further reduced and the conduction mechanism is dominated by carriers in the extended states.