Carbide contacts on homoepitaxial diamond films

We present experimental investigations of the structural and electrical properties of carbide contacts on homoepitaxial p-type diamond films in order to achieve Schottky diodes working at high temperatures with highly adhesive ohmic and Schottky contacts on diamond. For ohmic contacts, the reaction of molybdenum deposited by magnetron sputtering on homoepitaxial diamond layer is studied through X-ray diffraction and Rutherford backscattering. The formation of hexagonal α-Mo2C begins at 700 °C. However, the residual oxygen is exodiffused only at 900 °C and for undoped diamond. Nevertheless, ohmic contacts are achieved after annealing at 900 °C, with a low contact resistivity at a boron concentration of 1.6×1021 cm−3. For Schottky contacts, the in-situ reaction under ultra-high vacuum between Er and a non-oxidized diamond surface begins at 700 °C. A potential barrier height of 1.9 eV and a rectification ratio larger than 103 at 4 V at least up to 500 °C are obtained. In each case, coating layers intended to protect carbides against oxidation are assessed.