Uniform and thermally stable AuGeNi ohmic contacts to GaAs

An in situ rf sputter precleaning of the GaAs substrate before AuGeNi ohmic metal deposition yields contact resistance Rc=0.11 Ω mm at a peak doping of ∼1018/cm3. Excellent uniformity and thermal stability are achieved across the wafer. The contacts do not deteriorate appreciably after themal treatment at 410°C for 57 h.