Ohmic contacts to p- and n-type 4H-SiC using refractory alloyed W:Ni thin films were investigated. Transfer length measurement test structures to p-type 4H-SiC (NA = 3 ï¿½ 1020 cm-3) revealed Ohmic contacts with specific contact resistances, ρc, of ∼10-5 Ω cm2 after 0.5 h annealing in argon at temperatures of 1000 ï¿½C, 1100 ï¿½C, 1150 ï¿½C, and 1200 ï¿½C. Contacts fabricated on n-type 4H-SiC (ND = 2 ï¿½ 1019 cm-3) by similar methods were shown to have similar specific contact resistance values after annealing, demonstrating simultaneous Ohmic contact formation for W:Ni alloys on 4H-SiC. The lowest ρc values were (7.3 ï¿½ 0.9) ï¿½ 10-6 Ω cm2 for p-SiC and (6.8 ï¿½ 3.1) ï¿½ 10-6 Ω cm2 for n-SiC after annealing at 1150 ï¿½C. X-ray diffraction shows a cubic tungsten-nickel-carbide phase in the Ohmic contacts after annealing as well as WC after higher temperatures. Auger electron spectroscopy depth profiles support the presence of metal carbide regions above a nickel and silicon-rich region near the interface. X-ray energy dispersive spectroscopy mapping showed tungsten-rich and nickel-rich regions after annealing at 1100 ï¿½C and above. W:Ni alloys show promise as simultaneous Ohmic contacts to p- and n-SiC, offering low and comparable ρc values along with the formation of WxNiyC.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry