Dependence of implanted Se and S profiles on GaAs implantation temperature and crystallinity

Abstract

Atom depth distributions of Se implanted into GaAs show that the deep sides of the depth distributions are the result of interstitial diffusion of Se during implantation of crystalline GaAs. The effect saturates at an ion fluence of ∼1014 cm−2 for 25 °C implants and continues uninhibited up to the 1016 cm−2 fluence for 250 °C implantation temperature, implying that the GaAs implantation damage is annealed during implantation at 250 °C. Annealed Se profiles are unchanged for all fluences for both 25 and 250 °C implantation temperatures. Se implants into a self-amorphized GaAs surface yield more abrupt profiles than corresponding ones into crystalline GaAs, further indicating that when crystal channels are absent, implant tails are absent. Sulfur implants into crystalline and amorphized GaAs held at −130, 25, and 250 °C show that S behaves like Se for the unannealed case; the profiles for implants into crystalline GaAs are deeper the higher the substrate temperature during implantation, implying that diffusion or migration occurs during implantation. In contrast to the results for Se, the annealed S profiles redistribute significantly, characterized both by diffusion deeper into the GaAs and by redistribution toward the surface. These redistributions are significantly impeded by either a cold substrate temperature during implantation or by prior amorphization of the GaAs at any implantation temperature.