Intrinsic bistability in the resonant tunneling diode

Quantum transport in the resonant tunneling diode is modeled here with the Wigner formalism including self-consistent potentials for the first time. The calculated I-V characteristics show an intrinsic bistability in the negative differential conductivity region of the curve. We show that intrinsic bistability results from charge storage and the subsequent shifting of the internal potential of the device. The effect of undoped spacer layers is investigated. The cathode region of the RTD shows a strong depletion and quantization of electrons in a deep triangular potential well if no spacer layer is present. The potential drop in the cathode well reduces the barrier height to ballistic electron injected from the cathode, enhancing the valley current and reducing the peak-valley ratio. A finite relaxation time for the electrons increases the negative resistance, reduces the peak to valley ratio of the current, and causes a 'soft' hysteresis in the bistable region. The spacer layer prevents the formation of a deep quantum well at the cathode barrier, and the distribution does not deplete as sharply as without the spacer layer.