On the Schottky Barrier Height Lowering Effect of Ti3SiC2 in Ohmic Contacts to P-Type 4H-SiC

Abstract

In this paper, an experimental investigation into titanium (Ti) / aluminium (Al)-based ohmic contacts to p-type 4H-silicon carbide (SiC) has been presented. Electrical characterisation of the fabricated contacts showed that metal structures with an initial Ti layer yielded the lowest specific contact resistance (ρc), with a mean value of 3.7×10-5 Ω-cm2 being achieved after annealing in argon (Ar) at 1000°C for 2 minutes. Transmission electron microscopy (TEM) analysis illustrated the epitaxial relationship between the 4H-SiC and the as-deposited Ti layer, and, in conjunction with energy dispersive X-ray (EDX) analysis, showed that after annealing a ~5 nm thick layer of Ti3SiC2 was present, epitaxially arranged with the 4H-SiC. X-ray diffraction (XRD) analysis showed that the presence of the Ti3SiC2 metallic phase was more prevalent in the samples with Ti as the initial metal layer annealed at 1000°C, which corresponded with lower specific contact resistance. Fitting of experimental data to a thermionic field emission (TFE) model allowed the Schottky barrier height to be extracted; it was found that the lowest Schottky barrier heights were more prevalent where the most intense Ti3SiC2 phases were observed during XRD analysis.