Comparison of Pt-based ohmic contacts with Ti-Al ohmic contacts for p-type SiC

In this study, two Pt-based ohmic contacts were systematically compared with a conventional Ti-Al ohmic contact on p-type 4H- and 6H-SiC substrates in terms of specific contact resistance, contact morphology, and phase chemistry. The average specific contact resistance (SCR) values measured for the Ti/Al, Pt and Pt/Si ohmic contacts on 4H-SiC were 7.0 x 10(-5) Omega cm(2), 1.5 x 10(-4) Omega cm(2) and 4.4 x 10(-5) Omega cm(2), respectively. The corresponding standard deviations of the SCR values are 3.4 x 10(-5) Omega cm(2), 3.8 x 10(-5) Omega cm(2) and 1.3 x 10(-5) Omega cm(2). Microstructural analysis showed that both Ti/Al and Pt ohmic contacts reacted with the SiC substrate during annealing to form several phases and a rough interface. In contrast, single-phase PtSi contacts, formed using the required thickness ratio of 1 : 1.32 Pt/Si, yield a smooth interface. A correlation between the electrical properties and the morphology is discussed.