Dose rate effects on damage formation in ion-implanted gallium arsenide

Abstract

The residual damage in GaAs was measured by ion channeling following implantation of either 100 keV 30Si + at temperatures of 300 or 77 K, or 360 keV 120Sn + at 300 K. For room-temperature Si implants and fluences between 1 and 10 × 10 14Si/cm 2, the amount of damage created was strongly dependent upon the ion current density, which was varied between 0.05 and 12 μ |A/cm 2. Two different stages of damage growth were identified by an abrupt increase in the damage growth rate as a function of fluence, and the threshold fluence for the onset of the second stage was found to be dependent on the dose rate. The dose rate effect on damage was substantially weaker for 120Sn + implants and was negligible for Si implants at 77 K. The damage was found to be most sensitive to the average current density, demonstrating that the defects which are the precursors to the residual dose rate dependent damage have active lifetimes of at least 3 × 10 −4 s. The dose rate effect and its variation with ion mass and temperature are discussed in the context of homogeneous nucleation and growth of damage during ion irradiation.