OPTICAL AND ELECTRICAL CHARACTERISTICS OF GAAS IMPLANTED WITH HIGH-ENERGY (70 MEV) SN-120 IONS

Infra-red transmission and electrical characteristics of single crysta l GaAs substrates implanted with 70 MeV Sn-120 ions have been investig ated after implantation and subsequent annealing treatments. The optic al density ax is found to increase with implanted dose over photon ene rgy range 0.6-1.4 eV and reaches a high saturated value for the sample s implanted to a dose of 1 x 10(14) ions/cm(2). The saturation of alph a x versus hv suggests amorphisation. Annealing of higher dose samples above 350 degrees C reduces the density of the radiation defects. The deep lying states seem to be annealing out faster for the annealing t emperatures below 450 degrees C while annealing of near band edge dama ge occurs over the annealing temperature range of 450-600 degrees C. T he resistance values of the high dose (1 x 10(14) ions/cm(2)) samples which is initially low (less than or equal to 1 k Omega), are found to increase with annealing temperatures upto 650 degrees C and then decr ease for higher annealing temperatures. The resistance of the samples annealed up to 450 degrees C is dominated by variable range hopping co nduction below room temperature. For the samples annealed at temperatu res higher than 450 degrees C, the electrical transport is dominated b y hopping between the neighbouring defect sites. Above 650 degrees C a nnealing temperatures, the defect states are further reduced and the c onduction mechanism is dominated by carriers in the extended states. ( C) 1998 Elsevier Science Ltd. All rights reserved.