Scattering and Bloch oscillation in semiconductor superlattices

The transition between coherent and scattering-induced miniband transport i s observed. Hot electron spectroscopy is used to measure the superlattice t ransmittance at different bias conditions. For a short period superlattice the transmission is found to be independent of the direction of the electri c field. For a superlattice larger than the coherence length, the transmiss ion becomes asymmetric and dependent on the electric held direction. It is shown that interface roughness scattering enhances the transmission for pos itive bias. A fully three-dimensional calculation including interface rough ness scattering gives excellent agreement with experimental data. A coheren ce length of 150 nm and a scattering time of 1 ps are determined. (C) 1999 Elsevier Science B.V. All rights reserved.