Transition Between Coherent and Incoherent Electron Transport in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">GaAs</mml:mi><mml:mi>/</mml:mi><mml:mi mathvariant="normal">GaAlAs</mml:mi></mml:math>Superlattices

Abstract

The transition between coherent and incoherent transport in undoped $\mathrm{GaAs}/\mathrm{AlGaAs}$ superlattices is observed. Hot electron spectroscopy is used to measure the superlattice transmittance at different bias conditions. For a short-period superlattice the transmittance is found to be independent of the direction of the electric field. For a superlattice larger than the coherence length, the transmission becomes asymmetric and dependent on the electric field direction. The onset of scattering-induced miniband transport is clearly evident. A coherence length of 150 nm, limited by surface roughness, and a scattering time of 1 ps are determined.