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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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Silicon carbide (SiC), due to its thermal and electronic properties, has long been considered an excellent device material for microwave and millimeter-wave power generation. Numerical simulations were performed to study the typical power generating capabilities of SiC impact avalanche transit-time (IMP A TT) diodes utilizing the recent experimental data available. Operating characteristics of double-drift IMPATT devices at 10, 35, 60 and 94 GHz are compared. Both pulsed mode and continuous-wave (cw) mode operation are studied. Finally, a comparison among SiC, Si, and GaAs double-drift IMPA TT devices is made at various frequencies. It is shown that, for the pulsed mode of operation, SiC double-drift IMPA TT devices can produce significantly higher powers than Si and GaAs devices at comparable frequencies. In the cw mode of operation, SiC devices can produce significantly more power than GaAs devices at aU frequencies. However, a comparison at 94 GHz indicates that SiC IMP A TT diodes in the cw mode of operation produce power levels comparable to Si IMPA TT devices. At lower frequencies the performance of SiC diodes operating in the cw mode is expected to be better than the performance of Si devices due to the better thermal conductivity of SiC.

We present a numerical study of the I-X mixing in GaAs/AlAs/GaAs quantum well structures. A P-X mixing model proposed by Liu [Appl. Phys. Lett. 51, 1019 (1987)] is extended to include the effects of self-consistency and nonzero transverse momentum. In the present model, the coupled Schrodinger equations for I' and X electron envelope wave functions are solved self-consistently with Poisson's equation to calculate the electron transmission probability and wave functions, which lead to the current-voltage (I-V) characteristics of single barrier and double barrier resonant tunneling diode structures. The quantum transmitting boundary method is employed in the model for numerical solution of the coupled Schriidinger equations, which proves to be very stable and efficient, even for large (> 2000 A) structures. The features of I-X mixing, such as the resonance/antiresonance in the transmission probability and the virtual bound states, are clearly demonstrated. Additional physical features are observed in the transmission probability and the wave functions under applied bias conditions. Our work shows that inclusion of transverse momentum, variable effective mass, and the self-consistent potential is important in the realistic modeling of 1-V characteristics for structures exhibiting I-X coupling.

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Intrinsic bistability has been observed experimentally and attributed to the effect on the potential profile from stored charge in the quantum well through Poisson’s equation. This effect leads to two possible current states corresponding to a single voltage within the negative resistance region. In this letter a simulation method is presented which clearly shows bistability in the current-voltage curve of a resonant tunneling diode. This method self-consistently combines a Thomas–Fermi equilibrium model for the electron concentrations outside the double-barrier structure with a quantum calculation for the concentration inside the structure.