1. A gaseous precursor mixture from which semiconductor alloy material may be deposited by glow discharge decomposition: said mixture including a polysilane compound and a germanium-containing compound, said compounds capable of decomposing and depositing at substantially similar rates when subjected to electromagnetic energy; and said polysilane compound having the general formula Si.sub.x R.sub.y H.sub.z, where R is chosen from the group consisting essentially of hydrogen, fluorine, chlorine, iodine, bromine and combinations thereof, x is an integer greater than one, y and z are each an integer or zero, and y+z=2x+2.