Ohmic contacts to n-type GaAs using high-temperature rapid thermal annealing for self-aligned processing

We have formed Ge/Pd/W/Au and Ge/Mo/W/Au ohmic contacts to n-type GaAs by using a high-temperature rapid thermal annealing technique. The annealing schedule is compatible with that used for ion implantation activation, and the contact resistances (mid 10−6 Ω cm2) achieved are slightly higher than those for the commonly used Ni/Ge/Au alloyed contact. The Ge/Pd/W/Au contact maintains a good surface morphology and can be used as the implantation mask in self-aligned processes for devices such as heterojunction bipolar transistors.