Carrier activation in in situ Si-doped GaAs layers fabricated by a focused Si ion beam and molecular beam epitaxy combined system

C-V carrier profiles for 200 eV and 30 keV Si FIB singly and doubly implanted and successively buried regions in GaAs using a FIB/MBE combined system were investigated to show a possibility of formation of doping layer above the 30 keV Si-implanted region which is desirable for formation of three-dimensional semiconductor nano-structures. It is found that carrier density in the 30 keV Si implanted and buried region was reduced near the projected range and the doping efficiency was less than half of that in samples fabricated by implantation without the successive burying after post-annealing. For the 200 eV and 30 keV doubly implanted sample, the peak carrier density for 200 eV Si was reduced by 40% compared with 200 eV single implantation. The present result suggests that large amount of damage may be remained in the implanted range and the post-annealing was less effective in the buried sample because of the existence of the overlayer-regrown cap layer