Structural and electronic properties of hydrogen-terminated diamond field-effect transistors with h-BN gate dielectric featuring native point defects

High-mobility normally-off field-effect transistors (FETs) based on hexagonal boron nitride (h-BN)/hydrogen-terminated diamond (H-diamond) heterostructures and two-dimensional hole gas (2DHG) demonstrate tremendous potential. In this letter, we study structural and electronic properties of H-diamond FETs with h-BN gate dielectric featuring native point defects by first-principles calculations. The surface transfer doping model is applied to give theoretical insights into the energy band evolution of 2DHG H-diamond devices. In the case of a high electron affinity (EA) material acting as an electron acceptor on the H-diamond surface, the energy band on the H-diamond surface bends upwards. When a low EA material acts as a surface donor, the energy band on the H-diamond surface bends downward at this point. The local density of states for positive and negative valence defects in h-BN correspond to a downward and upward band bending on the H-diamond side, respectively. This result indicates that positive and negative valence defects in h-BN cause the h-BN/H-diamond heterostructure with different interfacial properties. The findings of this work can provide a rational design for improving the performance of diamond-based devices.