Leakage current reduction of normally off hydrogen-terminated diamond field effect transistor utilizing dual-barrier Schottky gate

Normally Off diamond field-effect transistor (FET) is demanded for energy saving and safety for practical application. Metal/diamond Schottky junction serving as the gate is a simple and effective approach to deplete holes under the gate, whereas low Schottky barrier height (SBH) is undesirable. In this work, a dual-barrier Schottky gate hydrogen,oxygen-terminated diamond (H,O-diamond) FET (DBG-FET) with Al gate was realized. Normally Off DBG-FET with enhanced SBH and reduced leakage was achieved. H,O-diamond, which was defined by x-ray photoelectron spectroscopy (XPS) technique, was realized by ultraviolet ozone (UV/O3) treatment with nanoparticle-Al mask. The enlarged SBH of 0.94 eV owing to the C-O bond minimized the diode reverse current and nicely shut down the DBG-FET at zero gate bias. Moreover, the forward current of diode can be well-reduced by hundred times ascribed to oxidized Al nanoparticles during the UV/O3 process. Based on this diode gate structure, the maximum drain current density, transconductance, on/off ratio, and subthreshold swing of the normally off DBG-FET are 21.8 mA/mm, 9.1 mS/mm, 109, and 96 mV/dec, respectively. The DBG-FET is expected to promote the development of normally off diamond FETs.