The role of Ni in the formation of low resistance Ni-Ge-Au ohmic contacts to n(+) GaAs heterostructures

Nickel is a commonly used wetting agent in alloyed Au-Ge ohmic contacts to n-GaAs, resulting in uniformity improvements to the morphology and contact resistance. In order to study the role of Ni in Ni-Ge-Au alloys, we have fa bricated samples with varying Ni content and characterized them using elect ron microbeam techniques. Our data indicate the amount of Ni in the alloy a ffects the microstructure and composition, the morphology of the metal/GaAs interface, and the amount of GaAs consumed during the alloy reaction. Also , the dopant distribution into the GaAs is heterogeneous depending on the a lloy microstructure.