High-performance H-diamond MOSFETs with compositionally graded Al-doped HfO2 gate dielectric

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Wide-bandgap semiconductors, particularly diamond, have been extensively investigated for next-generation electronic devices. In this work, hydrogen-terminated diamond (H-Diamond) metal–oxide–semiconductor field-effect transistors (MOSFETs) featuring a novel compositionally graded Al-Doped HfO 2 (HAO) gate dielectric were fabricated on single-crystal diamond substrates. The compositionally graded HAO layer, featuring a high Al content at the diamond interface and a high Hf content near the gate electrode, was deposited by atomic layer deposition at 250 °C. X-ray diffraction confirmed that the HAO films crystallize in the monoclinic phase. The fabricated devices exhibit favorable electrical characteristics, with a subthreshold swing as low as 83 mV·dec −1 and an ON/OFF current ratio exceeding 10 8 , indicating excellent gate controllability. Metal–insulator–metal capacitors based on the HAO dielectric achieve a breakdown field of 6.30 MV·cm −1 . These results demonstrate the feasibility of gradient Al-doped HAO as a gate dielectric for H-Diamond MOSFETs and offer a new strategy for crystalline-phase control of gate dielectrics on H-Diamond.