Abstract: Method of forming conductive members on a substrate of GaAs. Silicon is placed on the substrate surface in the desired pattern of the conductive members. The substrate is exposed to a gaseous atmosphere containing WF.sub.6. WF.sub.6 is reduced by the silicon causing tungsten to selectively deposit on the silicon but not on the exposed GaAs. The substrate is given a rapid thermal annealing treatment which causes the silicon-tungsten elements to form conductive members having a silicon rich layer at the bottom, an intermediate tungsten silicide layer, and a tungsten rich layer at the top. The conductive members form ohmic contacts with underlying heavily doped GaAs and rectifying Schottky barrier contacts with underlying lightly doped GaAs.