Diffusivities and activities of S implanted into GaAs through an As-doped a-Si:H film

Sulfur (S) ions are implanted at 500 keV into GaAs through 120 nm a-Si:H films doped with arsenic atoms at a concentration of 2×10 20 cm -3 . The samples are annealed in Ar gas at temperatures of 700–1000°C for 15 min. The sheet carrier concentration increases with increasing implant dose and annealing temperature. The diffusivity of the S atoms decreases with increasing implant dose. Silicon (Si) atoms are also doped from the a-Si:H films into GaAs during annealing and S + implantation. The distribution of the Si atoms becomes slightly shallower as the implant dose increases. The carrier concentrations, however, are left unchanged by Si doping.