Freeze-out effects on NMOS transistor characteristics at 4.2 K

Detailed substrate current characteristics of nMOSTs at 4.2 K were obtained with a view to elucidating their transient (hysteresis) and kink behavior below carrier freeze-out. A great similarity with room-temperature behavior is found, indicating that analogous expressions for the substrate current I_B can be used to calculate the transient time constant that follows from the forced depletion layer formation (FDLF) model reported previously by the authors (see ibid., vol.ED-35, p.1120-5, 1988). In a second part to this work, it will be demonstrated that both the substrate and the cooling bias have a marked influence on the kink. These effects can be fully understood with the FDLF model