Extinction of Random Telegraph Switching by “Cryogenic Annealing” in Small Area Si MOS Transistors*

Random telegraph switching (RTS) showing a slow decay in switching rate at cryogenic temperatures that leads to eventual extinction of the discrete fluctuations has been observed in the drain-source current (I_DS) of small area Si n-channel metal-oxide-semiconductor (NMOS) transistors. The RTS was characterized by I_DS fluctuations between two discrete levels over a finite interval of gate bias. In all devices showing RTS, the average switching rate gradually diminished to zero over a time of 1 to 2 hours at 15 K while maintaining nearly constant fluctuation amplitude, so that the RTS eventually ceased. This decay in switching rate may be due to a metastable oxygen vacancy defect that gradually repairs itself after repeated capture and emission of charge. Once gone, RTS did not reappear in any subsequent measurements even after bias and temperature cycling, suggesting a mechanism to deactivate at least some forms of RTS through a “cryogenic anneal”.