Low specific contact resistance on epitaxial p-type 4H-SiC with a step-bunching surface

This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the Al:Ti composition with no more than 50 at.% Al. The specific contact resistance (SCR) is obtained to be as low as 2.6×10^-6 Ω·cm² for the bilayered Ti(100 nm)/Al(100 nm) contact treated with 3 min rapid thermal annealing (RTA) at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti₃SiC₂ dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti₃SiC₂ layer with (0001)-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.