Carrier profile of the Si-doped layer in GaAs fabricated by a low-energy focused ion beam/molecular beam epitaxy combined system

Buried Si-doped layers in GaAs were fabricated by low-energy focused Si2+ i on beam (Si FIB) implantation in GaAs grown by molecular beam epitaxy (MBE) and successive overlayer regrowth using an FIB/MBE combined system, Carrie r profiles were measured by means of a capacitance-voltage profiling techni que. It was found that doped layers with a carrier concentration of 1.2 x 1 0(12) cm(-2) and a width (full width at half maximum) of 23 nm were formed without postannealing for the 200 eV Si implantation at: a dose of 7 x 10(1 2) cm(-2). After postannealing, the doping efficiency was improved and the width became narrower. At a dose of 1.4 x 10(13) cm(-2), narrower carrier d istribution with higher peak density was' observed although the total dopin g efficiency was decreased. In contrast a deeply depleted layer was formed and no carriers were observed for implantations at an energy higher than 40 0 eV before the postannealing. This may be because damage is significantly reduced for the lower implantation energy. (C) 1999 American Vacuum Society . [S0734-211X(99)19206-0].