Simulation of quantum transport in memory-switching double-barrier quantum-well diodes.

Abstract

Recent experiments on GaAs/AlAs double-barrier diodes incorporating ${\mathit{n}}^{\mathrm{\ensuremath{-}}}$/${\mathit{n}}^{+}$/${\mathit{n}}^{\mathrm{\ensuremath{-}}}$ spacer layers have shown that they exhibit two conduction curves that remain distinct across zero bias. Such devices can be reversibly switched between the two conduction curves and retain memory of the curve last switched to, even after short-circuit conditions. In this paper, we model the memory-switching phenomenon using a quantum kinetic formulation based on the Wigner distribution function. To obtain accurate Wigner distribution functions, an improved four-point difference scheme with an upwind bias is used to model the drift term in the equation of motion. The calculations result in two equilibrium (zero-voltage) states in double-barrier diodes incorporating ${\mathit{n}}^{\mathrm{\ensuremath{-}}}$/${\mathit{n}}^{+}$/${\mathit{n}}^{\mathrm{\ensuremath{-}}}$ spacer layers. Associated with each equilibrium state is a distinct and stable conduction curve. This work is a step toward an understanding of the more complex aspects of the phenomenon, such as state switching when the device is driven far from equilibrium.