Abstract
Unstable space-charge-waves in superlattice miniband transport are investigated using a modified drift-diffusion model and using a simplified one-dimensional hydrodynamic balance-equation formulation with a relaxation-time approximation. We point out that the earlier widely accepted notion, that in the small wavevector limit the space-chargewave (SCW) propagates at a phase velocity equal to the carrier drift velocity and with an amplitude-growth rate equal to the negative value of the mobility frequency, -ω c, was crucially based on the implicit assumption that the system momentum relaxation time τm is extremely small. Taking account of a finite momentum relaxation time, we find that even the drift-diffusion model would yield results significantly different from the above predictions: the phase velocity of a long-wavelength traveling SCW can be much slower than the carrier drift velocity and its amplitude-growth rate much smaller than -ωc. A hydrodynamic balance-equation formulation, which properly treats energy dissipation and further reduces the amplitude-growth rate, provides a convenient tool for improved qualitative analyses in SCW-related problem in semiconductor superlattices.
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Lei, X., Horing, N., Cui, H.L. et al. Superlattice space-charge-wave analyses in a modified drift-diffusion model and in a simplified balance-equation formulation. Zeitschrift für Physik B Condensed Matter 104, 221–225 (1997). https://doi.org/10.1007/s002570050443
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DOI: https://doi.org/10.1007/s002570050443