Self-consistent study of the resonant-tunneling diode.

Abstract

Quantum transport in the resonant-tunneling diode (RTD) is modeled here with the Wigner formalism including self-consistent potentials for the first time. We examine the computational aspects of the Wigner-function approach and the boundary conditions for the model. The calculated I-V characteristics show an intrinsic bistability in the negative-differential-conductivity region of the curve. Intrinsic bistability results from charge storage and the subsequent shifting of the internal potential of the device. The cathode region of the RTD shows a strong depletion and quantization of electrons in a deep triangular potential well, which reduces the barrier height to a ballistic electron injected from the cathode, enhancing the valley current and reducing the peak-to-valley ratio. Undoped spacer layers prevent the formation of a deep quantum well at the cathode barrier, and the distribution does not deplete as sharply as without the spacer layer. The I-V curve with the spacer layers shows a much lower negative resistance, and a sharper bistable region. 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. A zero-bias anomaly is found to result from high-momentum tails in the distribution at the barrier interface. These high-momentum tails contribute a small high-conductance current. The transient current during switching from the peak to the valley of the I-V curve shows inductive behavior and negative resistance for frequencies below 2 THz.