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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.

Interfacial reactions in nickel/titanium ohmic contacts to n -type silicon carbide Thermal stability and performance reliability of Pt/Ti/WSi/Ni ohmic contacts to n-SiC for high temperature and pulsed power device applications Improved Ni based composite Ohmic contact to n-SiC for high temperature and high power device applications

Ohmic contacts to n-type 4H-and 6H-SiC without postdeposition annealing were achieved using an interlayer of epitaxial InN beneath a layer of Ti. The InN films were grown by reactive dc magnetron sputtering at 450°C, whereas the Ti films were deposited by electron-beam evaporation at room temperature. The InN films were characterized by x-ray diffraction (XRD), secondary electron microscopy (SEM), cross-sectional transmission electron microscopy (TEM), and Hall-effect measurements. Both XRD and TEM observations revealed that the Ti and InN films have epitaxial relationships with the 6H-SiC substrate as follows: (0001)[11 " 20] Ti jj(0001)[11 " 20] InN jj (0001)[11 " 20] 6H-SiC . The Ti/InN/SiC contacts displayed ohmic behavior, whereas Ti/SiC contacts (without an InN interlayer) were nonohmic. These results suggest that InN reduces the Schottky barrier height at the SiC surface via a small conductionband offset and support previous reports of an electron accumulation layer at the surface of InN.

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