Total-Ionizing-Dose Response of MoS2 Transistors With ZrO2 and h-BN Gate Dielectrics

The total-ionizing-dose response of few layer MoS
₂
transistors with ZrO
₂
or h-BN gate dielectrics is investigated under various bias conditions. Defects in MoS
₂
and surrounding dielectric layers significantly affect radiation-induced trapping. For devices with ZrO
₂
dielectrics, much larger negative Vth shifts and peak transconductance degradation are observed for irradiation under negative and ground bias than under positive bias. The h-BN devices exhibit positive threshold voltage shifts under negative-bias irradiation. For both ZrO
₂
and h-BN passivated devices, the peak transconductance degradation results from charge trapping at the surface of the MoS
₂
or in nearby oxides. Changes in defect energy distributions of MoS
₂
FETs during X-ray irradiation are characterized via temperature-dependent low-frequency noise measurements. Density functional theory calculations are performed to provide insight into the pertinent defects.