Normally-off boron-doped diamond MOSFETs with a breakdown voltage over 1.7 kV

Boron-doped diamond (B-diamond) metal–oxide–semiconductor field-effect transistors (MOSFETs) are fabricated on a 150 nm-thick epitaxial layer. The threshold voltage of the B-diamond MOSFET is measured at −8.0 V, indicating a normally-off behavior. Due to the high activation energy for the boron dopants and the relatively thin epitaxial layer, a limited number of holes are formed in the B-diamond and potentially trapped within the Al2O3/B-diamond interface, leading to the normally-off behavior observed in the B-diamond MOSFET. The absolute breakdown voltage for the B-diamond MOSFET is found to exceed 1.7 kV. When divided by the gate-to-drain electrode length of 11.3 μm, the breakdown field is calculated to be 1.52 MV/cm, which is more than two times larger than that of the previous B-diamond MOSFETs.