ELECTRICAL-PROPERTIES OF INHOMOGENEOUS SIC MIS STRUCTURES

Current-voltage characteristics of metal contacts on 6H-SiC with a thin (5-20 Angstrom) oxide layer have been measured in the temperature range 300 to 1000K. The contacts were investigated in both H-2 and O-2-atmospheres. As the SiC surface was nonideal due to pin holes and other defects generated during the growth process, it was necessary to treat the Schottky contacts as inhomogeneous contacts. The inhomogeneity explains the nonideal current-voltage behavior of the contacts such as ideality factors much larger than unity and voltage dependent ideality factors. It was found that some metals gave Schottky contacts in the entire temperature range, while other metals were ohmic at higher temperatures. Several different contact metals were investigated: Al, Ti, TaSix, and Pd were found to be ohmic at high temperatures, while Pt, Pt+Cr, Ni, Cr and another TaSix contact were found to behave like Schottky contacts in the entire temperature range. This is a preliminary investigation of the electrical characteristics of different metals that could be useful for high temperature gas sensor purposes.