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Numerical solution of the time-dependent Schrödinger equation for resonant-tunneling diodes has been impeded by the difficulty in handling open-system boundary conditions. This paper presents a boundary condition method to simulate the interaction with ideal particle reservoirs at the device boundaries. A switching transient is calculated where the device is switched from the peak current state to the valley current state. In addition, this method was used to develop a small-signal analysis of resonant-tunneling diodes. Results for the small-signal equivalent circuit of a particular device versus frequency are presented.

Wigner function simulations of structures with experimentally observed high peak-to-valley ratios are carried out. It is shown that if care is taken with the numerical method used, the simulations reproduce these sharp resonances. When scattering is ignored, peak-to-valley ratios of 33.7 are obtained for a pseudomorphic InGaAs-AlAs structure. The effects of phonon scattering are included to first order. Also, a small-signal analysis is carried out and the results are used to predict the rf power generation capability of these devices.

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