REENTRANT RESONANT-TUNNELING

We study the effect of electron-electron interactions on the resonant- tunneling spectroscopy of the localized states in a barrier. Using a s imple model of three localized states, we show that, due to the Coulom b interactions, a single state can give rise to two resonant peaks in the conductance as a function of gate voltage, G(V-g). We also demonst rate that an additional higher-order resonance in between these two pe aks become possible due to the resonant-tunneling process involving tw o-electron transitions. We have observed both these effects in GaAs tr ansistor microstructures by studying the time evolution of three adjac ent G(V-g) peaks caused by fluctuating occupancy of an isolated impuri ty (modulator).