Effect of crystal stoichiometry on activation efficiency in Si implanted, rapid thermal annealed GaAs

A dramatic dependence on crystal stoichiometry has been observed for the donor activation efficiency of low doses of Si ions implanted into undoped semi-insulating GaAs. Samples from liquid encapsulated Czochralski crystals grown from melts containing As concentrations varying from 47 1/2 to 65 at. % were implanted with 100 keV 29Si ions at a dose of 5×1012 cm−2. Following a rapid, capless annealing cycle (950 °C, 5 s), the surface-depletion corrected activation efficiency ranged from 26 to 91%, with the higher efficiencies for higher As concentrations. In contrast, co-implantation of As and Si into standard (50 at. % As) GaAs resulted in an increase in activation efficiency from 59 to 68% for optimum As doses.