Gate-Controlled NiO/Graphene/4H-SiC Double Schottky Barrier Heterojunction Based on a Metal-Oxide-Semiconductor Structure for Dual-Mode and Wide Range Ultraviolet Detection

Based on a metal-oxide-semiconductor (MOS) structure, a double Schottky barrier junction (SBJ) made of NiO/graphene/4H-SiC is built and employed in ultraviolet (UV) detection. The hole concentration of NiO can be modulated as depleted or accumulated states with gate voltages, which allows the device to work in dual-mode when used as a photodetector. In this work, a negative gate bias causes the device to operate as a photoconductive detector with gain due to the negligible Schottky barrier, whereas a zero or positive gate bias makes it work as a Schottky photodiode. The device has a high responsivity of 103.3 A/W and a gain of 490.8 despite the low light intensity (261 nm laser @ 30.19 μW/cm2) at VDS = 5 V and VGS = −3 V. The NiO layer and SiC substrate both serve as UV absorption materials and produce photogenerated carriers, and the device has a wide UV response range from 240 to 400 nm with a gain of 80.34 when VDS = −3 V and VGS = 0 V at 240 nm. The above findings suggest that this MOS-based NiO/graphene/4H-SiC double SBJ has a great prospect in practical UV detection.