Metal-semiconductor field-effect transistors on hydrogen-terminated diamond surfaces

High-performance metal-semiconductor field-effect transistors (MESFETs) have been fabricated using p-type surface semiconductive layers on hydrogen-terminated surfaces of homoepitaxial CVD diamond films. In addition, their dc operation has been evaluated by device simulations to investigate the device operation mechanism. The fabricated MESFETs have been operated in both enhancement and depletion modes by selecting the electronegativity of the gate metal. The MESFETs exhibit complete channel pinch-off and drain-current saturation. The best transconductance for each mode of MESFETs exceeds 10 mS/mm with a gate length of 3∼7 μm. In the device simulations, a model of the surface semiconductive layer in which acceptors are distributed two-dimensionally on the surface reproduces well the actual dc characteristics. Based on this model, the simulations for a gate length of 1 μm have also been carried out to predict the operation of smaller devices. It was found that their transconductances exceed 100 mS/mm.