NiO_x Schottky-gated ZnO nanowire metal-semiconductor field effect transistor: Fast logic inverter and photo-detector

We demonstrate a high performance ZnO nanowire (NW) metal-semiconductor field effect transistor (MESFET) using semi-transparent NiO_x as a Schottky gate (SG), which shows excellent carrier mobility, on/off ratio, and sub-threshold slope of 301 cm² V^-1 s^-1, 10 ⁶, and 60 mV per decade, respectively. Based on the MESFET device cells, we fabricated one-dimensional (1D) logic NOT, NAND, and NOR gate circuits. The NOT gate inverter showed a high voltage gain of ∼16 under a supply voltage of 5 V and also displayed an excellent voltage inverting dynamics of at least a few kHz. In addition, attributed to the intrinsic sub-band gap defects at the transparent SG NiO_x/ZnO interface, our MESFET displayed good responses to visible light with a photo-gain of 7 × 10 ⁴. The persistent photoconductivity issue which originates from oxide semiconductor interfaces in general was initially present but was resolved by increasing the gate-source voltage of MESFET toward reverse bias.