Electrical Characteristics of 100 MeV 28Si implantation in GaAs

Single crystal n-GaAs substrates have been implanted at room temperature with 100 MeV 28Si ions to a dose of 1times1018 ions/m2. The electrical behaviour of these samples has been investigated after implantation and annealing to 850degC by current voltage (I-V) measurements. The I-V curves show series of complex behaviours with annealing treatments. To understand this complex behaviour, Resistance measurements of these samples using I-V measurements were carried out in the temperature range 100-300 K, which indicate that the as implanted sample and samples annealed to 350degC are dominated by a variable range hoping conduction mechanism, where as for the samples annealed at 450degC and 550degC the electrical conduction is due to hopping between the neighboring defect sites. The electrical transport for the sample annealed at 650degC seems to be dominated by carriers in the extended states. At annealing temperature higher than 650degC, the I-V characteristics are insensitive to measurement temperatures which indicates that the backward diode like structure after 850degC annealing is due to the activation of Si ions and formation of n+ region at the mean ion range and the existence of defect complex p+-type conductivity immediately above that region.