Theoretical study of the interface engineering for H-diamond field effect transistors with h-BN gate dielectric and graphite gate

Diamond has compelling advantages in power devices as an ultrawide-bandgap semiconductor. Using first-principles calculations, we systematically investigate the structural and electronic properties of hydrogen-terminated diamond (H-diamond) (111) van der Waals (vdW) heterostructures with graphite and hexagonal boron nitride (h-BN) layers. The graphite/H-diamond heterostructure forms a p-type ohmic contact and the p-type Schottky barrier decreases as the number of graphite layers increases. In contrast, the h-BN/H-diamond heterostructure exhibits semiconducting properties and a tunable type-II band alignment. Moreover, the charge transfer is concentrated at the interface with a large amount of charge accumulating on the C–H bonds on the H-diamond (111) surface, indicating the formation of a highly conductive two-dimensional hole gas (2DHG) layer. In a similar vein, the promising structural and electronic properties of graphite, h-BN, and H-diamond (111) in the graphite/h-BN/H-diamond (111) vdW heterostructure are well preserved upon their contact, while such heterostructure exhibits flexible band offset and Schottky contacts. These studies of interface engineering for H-diamond heterostructures are expected to advance the application of 2D materials in H-diamond field effect transistors, which is an important development in the design of surface transfer doping for 2DHG H-diamond devices.