Impact of low carbon concentrations on the electrical properties of highly boron doped SiGe layers

We present results on the effect of carbon coevaporation by molecular beam epitaxy on electrical properties of highly boron doped SiGe:C layers for C concentration of around 10(20) cm(-3). Such C concentrations are needed for substantial suppression of boron outdiffusion. The concentration of electrically active boron and the hole mobility are not affected by the addition of carbon. Carbon-related defects, typically observed for C concentrations below the bulk solid solubility limit (<10(18) cm(-3)), do not significantly reduce the concentration of electrically active B in SiGe:C. However, carbon coevaporation affects carrier lifetimes. The generation lifetime is reduced by more than one order of magnitude in SiGe:C compared with analogous SiGe layers. (C) 1997 American Institute of Physics.