Hydrogen-terminated diamond surfaces, emerging as a promising two-dimensional (2D) electron platform with great thermal and electronic properties, hold great potential for the next-generation high power and high frequency field effect transistor (FET). However, ideal gate dielectrics with high crystallinity and defect-free surfaces are still largely elusive. In this work, using the contamination-free pickup transfer method, hexagonal boron nitride (h-BN) flakes were fabricated on top of the hydrogen-terminated diamond surface to serve as a gate material and the passivation layer. The morphological and optical characterizations revealed the formation of homogeneous and intimate interface between h-BN and diamond. Benefiting from the h-BN gate dielectric layer, the maximum drain current density, subthreshold swing, and on/off ratio of diamond FET are measured to be −210.3 mA mm−1, 161 mV/dec, and 106, respectively. Especially, the transport measurement shows an almost constant Hall mobility of around 260 cm2 V−1 s−1 in the hole density range of 2 − 6 × 1012 cm−2, suggesting the excellent gate controllability of h-BN. Our results indicate that h-BN could form high-quality interface with hydrogen-terminated diamond, paving the way for the development of diamond-based electronic applications.

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