Dose rate effects on damage accumulation in Si+-implanted gallium arsenide

Ion-induced damage accumulation has been measured as a function of ion dose and dose rate following 100 keV Si+ room-temperature implants in GaAs. The dose rate has been found to have a strong effect on the total damage produced in GaAs over a range of dose between 1014 and 1015/cm2 and implantation current densities from 0.05 to 12 μA/cm2. Two distinct stages of damage formation have been identified. At low implantation doses, damage accumulates slowly and tends to saturate at a level of approximately 0.4x1017defects/cm2. However, beyond a threshold dose (∼1014 Si/cm2) which decreases with increasing dose rate, damage accumulates rapidly. In the second stage, the onset of which appears to be associated with the formation of more complex damage structures, the total damage and the damage accumulation rate were found to increase with dose rate for a fixed ion dose. For comparison, dose rate effects were also measured in Si and Ge under similar implant conditions and found to be weaker. The results for GaAs are correlated with recent observations of dose-rate-dependent electrical activation in Si-implanted GaAs