Resonant tunneling with a time-dependent voltage

The effects of an ac component in the voltage across a double-barrier structure are investigated in a simple model. The transmission probability for an incoming electron is calculated as a function of time. When the period of the ac voltage is short compared with the lifetime of an electron in the quantum well, photon-assisted tunneling occurs. In the opposite case, when the ac-voltage period is long, the transmission probability is governed by the instantaneous value of the voltage. In an intermediate regime, interesting interference effects, similar to effects seen in level-crossing problems, show up. We also calculate the time-dependent current through the structure.