Maximum tunnelling distance in MNOS devices theory
A.V. Ferris-Prabhu · physica status solidi (a) · 1972
Previous theories of the direct tunnelling mode behaviour of MNOS memory devices have assumed a monoenergetic trap distribution and have variously predicted that the time dependence of the total charge transfer is either exponential, assuming all tunnelling to occur from a fixed distance, or logarithmic, assuming that the trap density is constant through the entire thickness of the nitride. We first show that the former theory is a special case of the latter. To remove an internal inconsistency from this model we then postulate that the trap density is negligible beyond some maximum tunnelling distance. From this simple concept a more general and physically satisfactory result is derived which incorporates the previous ones, and predicts a value of approximately 34 Å for the maximum tunnelling distance.