Demonstration of Intrinsic Tristability in Double-Barrier Resonant Tunneling Diodes With the Wigner Transport Equation

The operation of double-barrier resonant tunneling diodes (RTDs) is investigated through self-consistent numerical solution of the Wigner transport equation. Prevalent boundary conditions are demonstrated to lead to unphysical boundary layers in electrostatically self-consistent calculations. New boundary conditions based on nonequilibrium statistics are proposed and validated. Unphysical solutions are also associated with the application of the popular Boltzmann collision operator in the limit of high electron density. An original formulation of the collision operator in the relaxation time approximation is proposed leading to proper asymptotic behavior in both limits of the relaxation time. Coupled solutions of the Wigner transport equation and the Poisson equation for an RTD structure reveal current to be a continuous but multivalued function of applied bias and tristability to be an intrinsic property of device operation.