WO3 Passivation of Access Regions in Diamond MOSFETs

We study the impact of access region passivation on the electrical characteristics of hydrogen-terminated diamond MOSFETs with tungsten Carbide (WC) edge contacts. Our experiments reveal a significant improvement to both contact and extrinsic channel sheet resistance once the access regions are passivated with WO
₃
, indicating that WO
₃
is an effective surface transfer-doping agent. We analyze a peculiar bump that appears in the subthreshold characteristics of the devices that prevents their effective turn-off. The bump is found to be mitigated when the access regions are passivated by WO
₃
. Poisson–Schrödinger (P–S) simulations suggest that this bump arises from the field-effect action by the gate over the access region immediately adjoining the gate. This parasitic field effect arises when the surface is unpinned and with a light hole concentration. Owing to its increased surface transfer doping, the use of WO
₃
as surface passivation is effective in delivering a sharp device turn-off.