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 VGS = −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 VGS 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 ≤ VGS ≤ −7 V. The maximum drain current density with 6 μm-gate length was −112 mA/mm at VGS of −7 V. These results will provide an approach for fabricating high-performance H-diamond FETs.