Al/Ni And Al/Ti Ohmic Contact To P-type SiC Diffused Layer

Abstract

Ohmic contacts to p-type SiC were fabricated by depositing Al/Ni and Al/Ti followed by high temperature annealing. A p-type layer was fabricated by Al or B diffusion from vapor phase into both p-type and n-type substrates. The thickness of the diffused layer was about 0.1–0.2 μm with surface carrier concentration of about 1.0×1019cm−3. Metal contacts to a p-type substrate with a background doping concentration of 1.2×1018cm−3, without a diffusion layer, were also formed. The values of specific contact resistance obtained by Circular Transmission Line Method (CTLM) and Transfer Length Method (TLM) for the n-type substrate, and by Cox & Strack method for p-type substrate, respectively, varied from 1.3×10−4Ωcm2 to 8.8×10−3 Ωcm2. The results indicate that the specific contact resistance could be significantly reduced by creating a highly doped diffused surface layer.