Quantum confinement in silicon–germanium electron waveguides

Abstract We have simulated the electronic properties of silicon–germanium electron waveguides defined by selective etching on a SiGe heterostructure. In particular, we have investigated the dependence of quantum confinement and of one-dimensional subband separation on the waveguide width. Indeed, a larger subband separation means a larger dephasing length and larger electron mobility in the waveguide, and therefore increased possibilities of detecting mesoscopic transport effects. Accurate modelling of SiGe electron waveguides requires us to take into account the effect of strain in the SiGe heterostructure and of the interface states at the exposed SiGe surface, and to solve the Poisson–Schrödinger equation in two dimensions. Results are also shown for a structure in which a gate electrode is evaporated onto the SiGe waveguide, realizing a three-terminal device in which the gate voltage is used to control the number of propagating modes, and therefore the conductance of the channel.