A modified lucky electron model for impact ionization rate in NMOSFET´s at 77 K

The nonstationary effects of electrons at 77 K, in the high field saturation region of the MOSFET, are modeled by incorporating an appropriate electron temperature decrease (-ΔT_e) to the carrier energy, within the framework of a modified lucky electron model. For a thin oxide MOSFET (T_cx=5 nm, L₀=0.5 μm), ΔT_c is a function of the electric field in the saturation region, and increases rapidly with drain bias. However, for a thick oxide MOSFET (T_cx=12.5 nm, L_g=5 μm), ΔT_e=280 K is found to adequately describe the impact ionization rate. Our model also explains the crossover of the ionization rates in the thick oxide MOSFET at 77 K and 300 K