Doping and impurity compensation by ion implantation in a-SiGe films

This paper discusses the electrical properties of a-SiGe films (NGe∼2.2 at. %) prepared by co-evaporation of Si and Ge from separate sources and doped by ion implantation of substitutional impurities (B+ and P+), as well as the results of controlled impurity compensation by ion-beam doping. It was found that B+ and P+ implantation into a-SiGe films in the dose range 1.3×1014–1.3×1017 cm−2, followed by annealing at 350 °C, increased the conductivity of these films from 10−9 to 10−4 and to 10−5 S/cm for B+ and P+, respectively. The position of the Fermi level could be varied from (Ev+0.27) to (Ec−0.19) eV. These investigations indicate that compensation of pre-doped a-SiGe films by ion implantation is feasible and reproducible. It is also found that higher doping efficiency of a-SiGe films is obtained by using boron than by using phosphorus.