Approach to optimizing n-SiC Ohmic contacts by replacing the original contacts with a second metal

Abstract

Nickel (Ni) contacts to n-type silicon carbide (n-SiC) have good electrical properties, but the physical contact, and therefore the reliability, is poor. An approach is described for using the good electrical properties of Ni Ohmic contacts, while using another metal for its superior topological, mechanical, thermal, or chemical properties for the chosen application. In the present work, we show that once the Ni contact has been annealed, forming nickel silicides, it can be etched off and replaced by a second metal chosen for its desired properties. This second metal displays an as-deposited contact resistance as low as the original annealed Ni contact, indicating that the critical feature responsible for Ohmic contact formation has not been removed when the silicide phases were etched off. Not only does this approach provide more flexibility for optimizing the contact for a given application but it also provides some insight into the Ohmic contact formation mechanism.