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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 ×10-5 Ω cm2, 1.5 ×10-4 Ω cm2 and 4.4 ×10-5 Ω cm2, respectively. The corresponding standard deviations of the SCR values are 3.4 ×10-5 Ω cm2, 3.8 ×10-5 Ω cm2 and 1.3 ×10-5 Ω cm2. 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.