Enhanced channel mobility of hexagonal boron nitride/hydrogen-terminated diamond heterojunction field-effect transistor

Hydrogen-terminated diamond field-effect transistors (FETs) using a hexagonal boron nitride (h-BN) gate insulator were fabricated on a diamond surface with reduced surface roughness in the direction of source/drain electrodes. The diamond surface was prepared on a mesa structure using chemical vapor deposition with a low methane concentration. The hydrogen-terminated surface was laminated with the h-BN gate insulator without air exposure to prevent the adsorption of atmospheric surface acceptors. The hydrogen-terminated diamond FET exhibited a high mobility of ≈1000 cm2 V−1 s−1 at room temperature. We performed theoretical analysis on the temperature and carrier density dependences of mobility, which suggested that Coulomb and surface roughness scattering were effectively reduced. The high mobility obtained in this study indicates the high potential of diamond as a semiconducting material. This study can contribute to the future development of diamond devices.