Ternary TiAlGe ohmic contacts for <i>p</i>-type 4H-SiC

Abstract

Reduction of annealing temperature to prepare low resistance ohmic contact materials for p-type 4H-SiC was achieved by adding Ge to the conventional TiAl contacts. Although the binary TiAl contact is required to anneal at temperature as high as 1000 °C to convert Schottky to ohmic behavior after deposition of the Ti and Al layers on the SiC substrate, the GeTiAl contacts provided the specific contact resistance of about 1×10−4 Ω cm2 by annealing at temperature as low as 600 °C. This low annealing temperature is desirable to reduce the gate leakage current of the SiC devices. The GeTiAl ohmic contacts were thermally stable during isothermal annealing at 400 °C subsequently after preparing the ohmic contacts by annealing at 600 °C, which is also required by the device packaging process.