P-TYPE DOPING OF GAAS BY CARBON IMPLANTATION

The electrical properties of C-implanted [100] GaAs have been studied following rapid thermal annealing at temperatures in the range from 75 0 to 950-degrees-C. This includes dopant profiling using differential Hall measurements. The maximum p-type activation efficiency was found to be a function of C-dose and annealing temperature, with the optimum annealing temperature varying from 900-degrees-C for C doses of 5 x 1 0(13) cm-2 to 800-degrees-C for doses greater-than-or-equal-to 5 X 10( 14) cm-2. For low dose implants, the net p-type activation efficiency was as high as 75%; while for the highest dose implants, it dropped to as low as 0.5%. Moreover, for these high-dose samples, 5 x 10(15) cm- 2, the activation efficiency was found to decrease with increasing ann ealing temperature, for temperatures above approximately 800-degrees-C , and the net hole concentration fell below that of samples implanted to lower doses. This issue is discussed in terms of the amphoteric dop ing behavior of C in GaAs. Hole mobilities showed little dependence on annealing temperature but decreased with increasing implant dose, ran ging from approximately 100 cm2/V.s for low dose implants, to approxim ately 65 cm2/V.s for high dose samples. These mobility values are the same or higher than those for Be-, Zn-, or Cd-implanted GaAs.