Ultrahigh On/Off Ratio (110) Diamond Transistors with Exceptional Reproducibility of Normally Off Characteristics

The development of monolithic integrated energy-efficient complementary circuits is crucial for the large-scale application of wide bandgap semiconductor-based high-frequency and high-power field-effect transistors (FETs). However, the inferior performance of p-channel FETs attributed to low hole density and mobility presents a substantial challenge. Diamond is a promising candidate due to its excellent comprehensive electrical properties and high thermal conductivity. Here, we report the fabrication of normally off diamond FETs based on a low work function metal gate and (110) hydrogen-terminated diamond with high hole density. The use of high-quality SiO₂ layer ensures the complete depletion of the channel by the gate and offers high gating efficiency. Therefore, the developed devices demonstrate exceptional reproducibility of normally off characteristics with centrally distributed threshold voltages (-0.37 ± 0.3 V) and realize large current and voltage handling capabilities and low static standby power consumption in a synergic manner with record-high on/off ratio exceeding 10¹⁰, high current density (∼200 μA·μm^-1), ultralow off-state current (∼fA·μm^-1), and high breakdown voltage (-676 V). Additionally, the thermal desorption of negatively charged acceptors has been proven to significantly reduce carrier scattering. This work offers superior performance p-channel FETs for implementing energy-efficient complementary circuits, laying the groundwork for accelerated development in wide bandgap semiconductor power electronics.