Gate leakage suppression of normally-OFF diamond FET by employing MOS-MES hybrid gate structure

Normally-off filed-effect transistors (FETs) are critical for logical circuit and switch systems. However, the presence of two-dimensional holes in hydrogen-terminated diamond (CH diamond) makes most of regular CH diamond MOSFETs normally-ON operation, leading to energy loss. Metal-semiconductor (MES) FETs with Schottky gate are a good way to achieve normally-off CH diamond FETs, but have the disadvantage of high gate leakage current. In this work, a MOS-MES hybrid gate diamond FET with normally-off operation and low gate leakage current was fabricated by adding nanoparticles Al2O3 (nano-Al2O3) between Al/C-H diamond interface. The MES formed by Al/C-H diamond plays the role of realizing normally-off operation, and the MOS of Al/nano-Al2O3/C-H diamond is used to lower the gate leakage current. 100 % of hybrid gate devices displayed normally-off operation with threshold voltages ranging from −0.2 V to −1.2 V, as well as the gate leakage current is 103-106-fold lower than that of FET without nano-Al2O3. The hybrid gate structure is poised to become a part of the FET community.