PROGRAMMABLE DEVICES BASED ON CURRENT-INDUCED CONDUCTIVITY IN AMORPHOUS-SILICON ALLOYS

This article describes the phenomenon of current induced conductivity in hydrogenated amorphous silicon alloys and how the effect can be use d to change the electrical characteristics of metal-semiconductor-meta l structures. It is shown that current induced conductivity is consist ent with the generation of silicon dangling bond states which form a d efect band with the rate of generation driven by the energy released d uring hole-electron recombination. The defect states can be annealed o ut and the device returned to its original condition. Measurements sho w that the conductivity of devices can be changed in a predictable way by current stressing or annealing and the strong current dependence o f defect formation enables the low field conductivity to be measured w ithout changing its magnitude. Extensive work with devices made from s ilicon-rich silicon nitride indicates that current induced conductivit y can be used in programmable devices or sensors but writing speeds ar e slow when large changes in conductivity are required. The phenomenon is therefore more suited to parallel architectures. (C) 1998 Elsevier Science Ltd.