Interfaces have been prepared by depositing hydrogenated amorphous Si (a‐Si:H) onto in a silane plasma at 450°C and annealing at temperatures between 600° and 1050°C. Rutherford backscattering, secondary ion mass spectroscopy, and transmission electron microscopy analyses show that the resulting interface is metallurgically stable when the Si is undoped, while significant interdiffusion occurs when P or As are added to the Si. The Si diffusion into the is rapid ( at 1000°C) depends on concentration and increases with increasing P content in the Si. Ohmic contacts prepared using (semi‐insulating) annealed at 800° and 1050°C, gave contact resistance of , respectively.