Characterization of diamond metal-insulator-semiconductor field-effect transistors with aluminum oxide gate insulator

Metal-insulator-semiconductor field-effect transistors (MISFETs) with aluminum oxide as a gate insulator have been fabricated on a hydrogen-terminated diamond surface using its surface conductive layer. The aluminum oxide gate insulator was deposited on the diamond surface by the pulsed laser deposition method. The on-off ratio measured by dc was greater than five orders of magnitude, one of the best results reported for diamond FETs. The gate leak current of aluminum oxide MISFETs is three orders of magnitude less than that of conventional CaF₂ MISFETs. These characteristics indicate that aluminum oxide gate insulators are suitable for high reliability power device applications of diamond MISFETs.