Role of interface layers and localized states in TiAl-based ohmic contacts to p-type 4H-SiC

We have investigated the roles of interfacial reaction, work function variation, and localized states of annealed Ti/Al ohmic contacts to p-type 4H-SiC. The Al was found to be absent in the near interface region. The possibility of additional p-doping by Al indiffusion in the top SiC layer was ruled out. The work function of Ti3SiC2, the direct contact layer to SiC, was determined to be intermediate between Ti and p-SiC, leading to a considerably lowered Schottky barrier height. Reaction-induced interfacial states were observed in the near-interface SiC, which may further reduce the barrier height and cause the formation of ohmic contact.