ESTIMATION OF COTUNNELING IN SINGLE-ELECTRON LOGIC AND ITS SUPPRESSION

It is known that cotunneling causes a serious decline in the reliabili ty of single-electron logic circuits. We report the effects of cotunne ling on single-electron logic circuits studied using computer simulati on in which both two-electron cotunneling and normal single-electron t unneling are taken into account. It is proved that the cotunneling red uces the operation accuracy of single-electron logic circuits consider ably even at absolute zero. At finite temperatures both normal tunneli ng and cotunneling are enhanced by thermal fluctuation. Temperature de pendence of tunneling rates of both processes is also discussed. In or der to suppress cotunneling, we consider the tunnel resistance of junc tions as one of the design parameters and show that the cotunneling ra te can be reduced by optimizing the resistance. In addition, we presen t an inverter circuit that exhibits a better tolerance of the cotunnel ing effect.