A MONTE-CARLO APPROACH FOR INCORPORATION OF MEMORY EFFECT IN SWITCHEDGATE BIAS EXPERIMENTS

This article presents a Monte Carlo approach to simulate the dispersiv e transport of holes/H+ ions in silicon-dioxide using simplified forma lism of continuous time random walk theory given by Montroll and Scher [E. W. Montroll and H. Scher, J. Stat. Phys. 9, 101 (1973); H. Scher and E. W. Montroll, Phys. Rev. B 12, 2455 (1975)]. It has been shown t hat the simulated results of this approach match quite well with the t heoretical predictions for a value of dispersion coefficient, alpha, = 0.5 which validates our Monte Carlo simulator. We have used this simul ator to resolve the memory effect observed by Saks et al. [N. S. Saks, D. B. Brown, and R. W. Rendell, IEEE Trans. Nucl. Sci. 38, 1130 (1991 )] in their simulations of switched gate bias experiments in context w ith the hydrogen ion transport model for the buildup of radiation-indu ced interface states. We have accounted for the memory effect, which i s related with the dwell time of an ion at the last hopping site just before field switching, by treating the first hop after field switchin g differently from all other hops. We have shown that the memory effec t can be incorporated by modifying the value of cu only for the first hop after field switching depending on the dwell time at the last hopp ing site just before field switching. We have found that a logarithmic relationship between the two gives a very good match between the simu lated and the experimental results of half-time (the time required to build 50% of saturated interface states) versus time of field switchin g, t(switch), relationship. (C) 1998 American Institute of Physics.