Influence of hot-carrier stress on the kink/hysteresis behaviour of NMOST´s operating at liquid helium temperatures

In this paper the hot-carrier degradation behaviour of Si NMOST´s at 4.2K is reported. It is demonstrated that both reversible and irreversible changes are generated, which strongly depend on the stressing conditions. The unexpected reduction in threshold voltage and the anomalous increase in substrate current often observed after 4.2K stress in p-well devices is explained by considering the charging of the substrate, Similar effects are observed in SOI NMOST´s stressed at liquid helium temperatures (LHT).