Scattering and Bloch oscillation in semiconductor superlattices

The transition between coherent and scattering-induced miniband transport is observed. Hot electron spectroscopy is used to measure the superlattice transmittance at different bias conditions. For a short period superlattice the transmission 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. It is shown that interface roughness scattering enhances the transmission for positive bias. A fully three-dimensional calculation including interface roughness scattering gives excellent agreement with experimental data. A coherence length of 150 nm and a scattering time of 1 ps are determined. (C) 1999 Elsevier Science B.V. All rights reserved.