Schottky diode architectures on p-type diamond for fast switching, high forward current density and high breakdown field rectifiers

The electrical properties of Schottky contacts on the (100) surface of Boron doped diamond films epitaxially grown on Ib substrates are investigated in this work. The role of Boron doping concentration and extended defects detected by cathodoluminescence is correlated to current voltage characteristics, rectifying efficiency and high voltage performance of the diodes up to 1 kV and more. The influence of surface treatment prior to metal deposition is highlighted and the choice of metal for the Schottky contact is discussed. The paramount importance of using an oxidised diamond surface at the Schottky contacts and outside is demonstrated. Decreasing the series resistance of diodes is obtained with a stack of two layers, the upper one being lightly doped while the deeper one contains Boron concentrations close to the metallic conductivity threshold (4 × 1020 B/cm3). Several architectures are studied. The ohmic contact directly laid on the heavily doped layer permits forward current densities of 66 A/cm2 under 4 V at room temperature and switching times in the nanosecond range. This set of results shows that p-type diamond is an adequate semiconductor for implementing high speed, high power and high voltage electronic rectifiers.

Research Highlights
► Bulk and surface properties of diamond influence Schottky diode characteristics.
► Extended defects and Boron concentrations > 1016 B/cm3 worsen the reverse current.
► Electrical and chemical passivation of the free surface and interface are demonstrated.
► A stack of lightly and heavily doped layers leads to high forward current densities.
► Fast switching and high breakdown field rectifiers can be implemented on diamond.