Carrier distribution profiles in Si-doped layers in GaAs formed by focusedion beam implantation and successive overlayer growth

Selectively doped layers buried in GaAs were formed by low (50 and 200 eV) and high (30 keV) energy focused Si ion implantation and successive overlay er growth using a focused ion beam/ molecular beam epitaxy (MBE) combined s ystem to investigate the possibility to form patterned delta -doped layers. Carrier distribution profiles were measured by means of a capacitance-volt age profiling technique at room temperature. It was found for the low-energ y implantation that the width of the depth profiles of the carrier distribu tion decreased with increasing sheet carrier density and was roughly in agr eement with a theoretical estimation obtained by solving the Poisson equati on. The width was decreased when the sheet carrier density increased by ann ealing. This indicates that the width is determined by a sheet carrier dens ity and not by Si dopant profiles, and that narrower carrier profiles can b e formed by optimizing annealing parameters, although the widths were 2-5 t imes wider than those observed for the MBE-grown delta -doped GaAs. The sam e doping efficiency as for the low-energy implantation was achieved but the distribution width was close to that of the dopant distribution. (C) 2000 American Vacuum Society. [S0734-211X(00)06206-5].