Quantum confinement in silicon-germanium electronwaveguides

Abstract

We have simulated the electronic properties ofsilicon-germanium electron waveguides defined by selectiveetching on a SiGe heterostructure. In particular, we haveinvestigated the dependence of quantum confinement and of one-dimensionalsubband separation on the waveguide width. Indeed, a largersubband separation means a larger dephasing length and largerelectron mobility in the waveguide, and therefore increasedpossibilities of detecting mesoscopic transport effects. Accurate modelling of SiGe electron waveguides requires us to takeinto account the effect of strain in the SiGe heterostructureand of the interface states at the exposed SiGe surface, and tosolve the Poisson-Schrödinger equation in two dimensions. Results are also shown for a structure in which a gate electrodeis evaporated onto the SiGe waveguide, realizing athree-terminal device in which the gate voltage is used tocontrol the number of propagating modes, and therefore theconductance of the channel.