New Al-Ni-Ge Contacts on GaAs; Their Structure and Electrical Properties

Abstract

ABSTRACTThe structure and composition of the recently developed Al-Ni-Ge ohmic contacts to n-GaAs were investigated by transmission electron microscopy combined with secondary ion mass spectroscopy (SIMS) and Auger spectroscopy. The semiconductor/metal-alloy interface of these contacts remain very flat after annealing (500°C, for 1 min - contact resistance 1.4×10−6Ωcm2), in contrast to the widely used Au-Ni-Ge contacts. The metal sequence during deposition is found to be a critical factor in determining the electrical contact properties and the dispersion of the oxide layer on the semiconductor surface after chemical cleaning. Ge doping of the GaAs beneath the contact layer was observed by SIMS, and a tunneling mechanism through the n+GaAs:Ge layer was proposed to explain the ohmic properties of the contacts.