Impact of hole trap-detrap mechanism on X-ray irradiation induced threshold voltage shift of radiation-hardened GAA TFET device

Abstract

We demonstrate the X-ray irradiation effect on a radiation-hardened gate-all-around tunnel FET (GAA TFET) device. The radiation-hardened device has a high and fixed oxide electric field, which is responsible to attain equilibrium state of the device. Once the device reaches equilibrium, the threshold voltage starts to saturate for any variation in the gate bias. Therefore, the fixed electric field in the oxide region is reduced with the application of negative bias to the gate, which varies the equilibrium trapped charge concentration in the oxide. The negative gate bias causes electrons of oxide and holes from the bias terminal to recombine, which ultimately reduces the electric field in the oxide region. This variation in charge concentration results in a new threshold voltage when the device has been re-irradiated. Further, the unique carrier injection mechanism of the TFET device plays a significant role in trapping and detrapping mechanisms along the channel. The report consists of positive charge trapping and detrapping of charge carriers along the channel of the GAA-TFET device. In addition, the report also deals with the impact of applying excessive gate bias to the device and its impact on electric fields. For the X-ray irradiation analysis, several figures of merit are taken into consideration before coming to the conclusion of the report, such as geminate yield, trapped charges in the oxide region, and time-varying positive charge build-up in the oxide. The device under consideration has also been irradiated with several radiation doses and time durations to verify its robustness.