Formation of the intermediate semiconductor larger for the Ohmic contact to silicon carbide using Germanium implantation

By formation of an intermediate semiconductor layer (ISL) with a narrow band gap at the metallic contact/SiC interface, this paper realises a new method to fabricate the low-resistance Ohmic contacts for SiC. An array of transfer length method (TLM) test patterns is formed on N-wells created by P⁺ ion implantation into Si-faced p-type 4H-SiC epilayer. The ISL of nickel-metal Ohmic contacts to n-type 4H-SiC could be formed by using Germanium ion implantation into SiC. The specific contact resistance \rho_\rm c as low as 4.23× 10^-5 \Omega\cdotcm² is achieved after annealing in N₂ at 800 °C for 3 min, which is much lower than that (>900 °C) in the typical SiC metallisation process. The sheet resistance R_sh of the implanted layers is 1.5 k\Omega/\Box. The technique for converting photoresist into nanocrystalline graphite is used to protect the SiC surface in the annealing after Ge⁺ ion implantations.