The empirical dependence of radiation-induced charge neutralization on negative bias in dosimeters based on the metal-oxide-semiconductor field-effect transistor

The dependence of radiation-induced charge neutralization (RICN) has been studied in metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. These devices were first exposed to x rays under positive bias and then to further dose increments at a selection of reverse bias levels. A nonlinear empirical trend has been established that is consistent with that identified in the data obtained in this work. Estimates for the reverse bias level corresponding to the maximum rate of RICN have been extracted from the data. These optimum bias levels appear to be independent of the level of initial absorbed dose under positive bias. The established models for threshold voltage change have been considered and indicate a related nonlinear trend for neutralization cross section σ_N as a function of oxide field. These data are discussed in the context of dose measurement with MOSFETs and within the framework of statistical mechanics associated with neutral traps and their field dependence.