Total ionization dose effects of N-type tunnel field effect transistor (TFET) with ultra-shallow pocket junction

Abstract

N-type tunnel field effect transistors (TFETs) with Si1−xGex/Si hetero-junction in the ultra-shallow N+ pocket region have been fabricated. This paper investigates the total ionization dose (TID) effects on the electrical characteristics of these N-type TFET devices, including transfer and output characteristics, via a 60Co γ-ray irradiation source. TID has little impact on the on-state current for TFETs with and without P well. With the increase in total dose, however, a shift in the transfer characteristics, such as the off-state current and subthreshold slope is observed. Under the same TID condition, TFETs with P well exhibit more robustness as compared to TFETs without P well. The characteristics under room temperature and high temperature annealing conditions after irradiation are also investigated. The underlying mechanisms, such as the interplay among bulk trapped charge in gate oxide-induced inversion and interface trap-induced trap-assisted-tunneling, are identified by TCAD simulation and are discussed in detail.