Carrier removal in n-type GaAs layers by oxygen implantation analysed by positron annihilation spectroscopy

An n-doped layer in SI GaAs has been formed by silicon implantation and thermal activation. The subsequent removal of the charge carriers by multiple energy oxygen implantation has been analysed using positron annihilation spectroscopy. This technique allows lattice damage, and in particular vacancy-type defects, to be probed in the implanted region at concentrations ranging from 10¹⁶-10¹⁹ cm^-3. Damage levels have been measured for a range of annealing temperatures and compared to the sheet resistivity of the implanted layer. The insensitivity of the positrons to the implanted oxygen provides the capability of analysing the contribution of the vacancy type defects to the isolation. These results highlight the applicability of the positron technique to the study of other materials requiring implant isolation