Transport spectroscopy of quantum wires and superlattices

A new device based on side-gated wires demonstrates that the side gate wire technique can be successfully implemented as a novel selective depletion s cheme for vertical tunneling devices. Resonant tunneling between 1D states was achieved by an additional lateral confinement generated by a central ga te. From model considerations assuming a parabolic confinement, the tuning range of the subband energy was estimated to Lie between 0 meV and 5-6 meV. The transmittance of strongly coupled superlattices at different superlatt ice bias conditions is measured by varying the energy of the injected hot e lectron beam. The onset of scattering-induced miniband transport is clearly evident and the transition between coherent and incoherent electron transp ort in superlattices is observed for the first time. A coherence length of 150 nm and a scattering time of 1 ps is determined. The experimental result is in good agreement to a fully three-dimensional calculation including in terface roughness with typical island sizes of 10 nm. This clearly demonstr ates that interface roughness scattering Limits the coherence length of bal listic electrons in the superlattice. (C) 2000 Elsevier Science S.A. All ri ghts reserved.