Electrical properties of MgO/p-diamond junction fabricated on homoepitaxial single-crystalline diamond

Abstract Sufficiently flat and hillock-free insulating homoepitaxial diamond films were successfully grown on high-pressure–high-temperature-synthesized diamond using a 5-kW microwave-plasma chemical-vapor-deposition system with a 20-ppm-nitrogen-included source gas of 4% CH 4 diluted with H 2 . Then, layered MgO/boron-doped (p-type) diamond structures were fabricated on the homoepitaxial insulating diamond. Current ( I )–voltage ( V ) characteristics of these device structures showed strong nonlinear behaviors for both current directions, or those for two electrically-parallel, reversed diodes, with conduction limited mainly by sheet resistance of the p-diamond layer in a temperature range from 300 to 600 K. This suggests that the carrier transport occurred through different current passes in the junction region at both biases. Low-frequency capacitances measured were mainly dominated by the depletion capacitance which was influenced by the bias voltage. At relatively high frequencies, however, the total capacitance measured ( C ) was determined not only by the depletion capacitance but also by the series resistance and the dispersion capacitance. Equivalent circuits of the MgO/p-diamond structure were deduced to explain the measured I – V and C – V results. A possible conduction mechanism is proposed in relation to the electronic structure of the MgO/p-diamond junction.