Improved performance of H-diamond MOSFETs with ZrO₂/Al₂O₃ gate dielectric stacks deposited by electron beam method

H-diamond MOSFETs with ZrO₂/Al₂O₃ gate dielectric stacks were fabricated using an electron beam (EB) evaporation technique. The fixed positive charge in the ZrO₂ contact layer depleted the two-dimensional hole gas to achieve normally off operation. Thanks to the leakage suppression of Al₂O₃ blocking layer, the device exhibited a considerably low gate leakage current of 1.8 × 10⁻⁶ A/cm² at V_GS = −5 V. Contributed from the relatively lower estimated interfacial state density (1.45 × 10¹² cm⁻² eV⁻¹) and uncontaminated ZrO₂/Al₂O₃ gate interface, the maximum mobility was estimated to be 345.8 cm²/V·s at V_GS of −2 V, indicating excellent interfacial property of ZrO₂/H-diamond. The hole mobility remains an almost constant of about 150 cm²/V·s for −4 V ≤ V_GS ≤ −7 V. The maximum drain current density with 6 μm-gate length was −112 mA/mm at V_GS of −7 V. These results will provide an approach for fabricating high-performance H-diamond FETs.