Effect of incoherence on current and shot noise in resonant tunneling: An exactly solvable model

We describe an exactly solvable mode of a resonant-tunneling diode in which incoherence is introduced by adding a small random phase to the wave function on each round trip between the barriers—a Fabry-Pérot picture with dephasing. We find that this form of incoherence broadens and lowers the resonant transmission peak while conserving its area (current conservation), in agreement with previous studies. The autocorrelation function of the transmission coefficient cannot be characterized by a single width but has two energy scales, which we speculate may identify ‘‘coherent’’ and ‘‘incoherent’’ fractions of the current. The shot noise is raised from the suppressed value found for purely coherent transport towards its classical value. This behavior is supported by a picture using wave packets with differing transmision coefficients impinging on a barrier.