We propose a p-MoS2/HfS2 van der Waals (vdW) heterostructure tunneling field-effect transistor (TFET) with a type-II band alignment for future power-efficient electronics. The differences in temperature dependence between p-MoS2/HfS2 TFET and HfS2 metal-oxide-semiconductor field-effect transistor showed that the turn-on current of p-MoS2/HfS2 TFET originated from band-to-band tunneling. To suppress the impact of interface traps, reduce the subthreshold swing (SS), and increase the gate capacitance, the 25 nm Al2O3 gate dielectric was replaced with a 15 nm HfO2 layer. Additionally, a buried Ni back-gate structure was introduced to reduce the area of overlap between the gate, contact electrodes, and gate leakage along with the scaling of equivalent oxide thickness. Subsequently, enlargement of gate capacitance by three times led to the reduction of SS from 700  to 300 mV dec−1, which verified that increasing the gate capacitance suppressed the impact of interface traps and improved gate controllability in the vdW heterostructure TFET.

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In this study, we fabricated MOSFETs with Al2O3/InGaAs or HfO2/Al2O3/InGaAs gate stacks. The surface was subjected to nitrogen plasma and trimethylaluminum cleaning prior to low-temperature atomic layer deposition. Electron mobility was extracted using the capacitance–gate voltage (C–VG) and drain current–gate voltage (ID–VG) characteristics. We determined that the mobility decreased when the gate voltage sweeping width increased during C–VG and ID–VG measurements. In addition, we determined that the lowering of the deposition temperature to 120 °C improved the mobility of MOSFETs with HfO2/Al2O3/InGaAs gate stacks as compared with that corresponding to deposition at 300 °C. Furthermore, HfO2/Al2O3/InGaAs gate stacks with various Al2O3 thicknesses were fabricated. When the number of Al2O3 deposition cycles was more than 4, the mobility of MOSFETs with HfO2/Al2O3/InGaAs gate stacks improved, reaching the value of the Al2O3/InGaAs gate stack.