Chemical and Electrical Mechanisms in Titanium, Platinum, and Hafnium Contacts to Alpha (6H) Silicon Carbide

Abstract

ABSTRACTThin films (2 Å - 1000 Å) of titanium, platinum, and hafnium were deposited via UHV electron beam evaporation at room temperature on n-type, (0001) alpha (6H)-SiC and compared in terms of interfacial chemistry, energy barriers to electrical conduction, and macroscopic electrical behavior. Current-voltage measurements have shown that these contacts are rectifying, all with ideality factors between 1.01 and 1.09. The lowest leakage currents (∼5 × 10−8 A/cm2 at -10 V) were determined for unannealed Pt contacts and for Hf contacts annealed at 700°C for 20 minutes. Current-voltage (I-V), capacitance-voltage (C-V), and x-ray photoelectron spectro-scopy (XPS) were among the techniques used to determine barrier heights, all of which were within a few tenths of an electron volt of 1.0 eV. The narrow range of calculated barrier heights along with the XPS valence spectrum of the chemically prepared SiC surface give evidence that the Fermi level is pinned at the semiconductor surface.