DOPING AND IMPURITY COMPENSATION BY ION-IMPLANTATION IN A-SIGE FILMS

This paper discusses the electrical properties of a-SiGe films (N-Ge s imilar to 2.2 at. %) prepared by;2.2 co-evaporation of Si and Ge from separate sources and doped by ion implantation of substitutional impur ities (B+ and P+) as well as the results of controlled impurity compen sation by ion-beam doping. It was found that B+ and P+ implantation in to a-SiGe films in the dose range 1.3 x 10(14) - 1.3 x 10(17) cm(-2), followed by annealing at 350 degrees C, increased the conductivity of these films from 10(-9) to 10(-4) and to 10(-5) S/cm for B+ and P+, re spectively. The position of the Fermi level could be varied from (E-v + 0.27) to (E-c - 0.19) eV. These investigations indicate that compens ation of pre-doped a-SiGe films by ion implantation is feasible and re producible. It is also found that higher doping efficiency of a-SiGe f ilms is obtained by using boron than by using phosphorus. (C) 1998 Ame rican Institute of Physics. [S1063-7826(98)02410-7].