Theoretical Insights Into the Interface Properties of Hydrogen-Terminated and Oxidized Silicon-Terminated Diamond Field-Effect Transistors With h-BeO Gate Dielectric

Diamond surfaces provide an innovative platform for the exploitation of electronic devices. In this work, we investigate the structural and electronic properties of hexagonal beryllium oxide (h-BeO)/hydrogen, fluorine, oxygen, and oxidized silicon (H, F, O, O-Si)-terminated diamond (100) heterostructures by first-principles calculations. The results indicate that the h-BeO/(H, O-Si)-diamond heterostructures demonstrate lower binding energies and higher interfacial charge transfer compared to the h-BeO/(F, O)-diamond systems. Furthermore, the h-BeO/H-diamond heterostructure shows semiconducting characteristics with a direct bandgap of 4.80 eV, where the h-BeO layer forms a Type-II band alignment with the H-diamond surface. The resultant band offsets are 2.75 and 1.42 eV, indicating that h-BeO can be considered a high-quality gate dielectric material for 2-D hole gas (2DHG) H-diamond field-effect transistors (FETs). A low electron affinity is established on the (H, O-Si)-diamond surfaces and the h-BeO/(H, O-Si)-diamond interfaces form a downward band bend, which contributes to the formation of normally-OFF diamond FETs. This study provides an in-depth theoretical understanding of the normally-OFF characteristics for 2DHG diamond FETs and demonstrates the excellent potential of h-BeO on (H, O-Si)-diamond surface for diamond devices.