Limits of semiclassical transport in narrow miniband GaAs/AlAs superlattices

Abstract

We address in this work the electronic conduction properties of superlattices (SL) along the growth axis, in the limit of narrow minibands. Experimental results on a series of GaAs/AlAs SLs are compared to earlier data on wide miniband samples, and to theoretical velocity-field characteristics obtained from the solution of the Boltzmann equation. Negative differential velocity is systematically observed, and a remarkably regular variation of the peak velocity with the miniband width is found, in excellent agreement with calculations including realistic scattering. Semiclassical miniband conduction therefore appears to be an adequate description of transport between ∼ 77K and 400K, down to miniband widths of 4 meV in our samples. This unexpected result is discussed with respect to disorder localization and Wannier-Stark quantization.