A New Technique for Fabrication of Ohmic Contacts to GaAs Devices

Abstract

A simple technique for obtaining reproducible ohmic contacts to n-type GaAS is described. It is shown that a particular alloy of gold-germanium, when evaporated onto the hot substrate under specified conditions, yields ohmic contacts with extremely low series resistance. The contact resistance was then separated from the bulk resistance of the semiconductor. The specific resistance of contacts thus made was about 2.32 × 10-⁵ ohm-cm². The experimental observations are shown to be in close agreement with a theoretical model based on quantum mechanical tunneling. Phase diagrams and related metallurgical considerations are also discussed.