Electronic properties of nanowire superlattices in the presence of strain and magnetic-fieldeffects

Abstract

A calculation of the effective electron barrier potential in quantum-wire superlatticessubject to magnetic-field and strain effects is presented. It is shown that, besides thelateral-confinement contributions to the barrier potential emphasized by the authors inearlier work (Lew Yan Voon and Willatzen 2003 J. Appl. Phys. 93 9997; Lew Yan Voon et al 2004 J. Appl. Phys. 96 4660), strong contributions from strain (lattice mismatch) may bepresent as well. This is due to the fact that strain values can be several percent inheterostructures while electron deformation potentials are of the order of 10 eV. It is alsoshown that Landau and Landé magnetic-field contributions become important at magneticfields of 10 T or higher. The driving force behind the lateral-confinement and the Landaumagnetic-field contributions is the same, namely, the electron effective-mass difference inthe two material constituents forming the superlattice structure; however, thedependences of the two contributions on lateral dimensions are inverse squared andsquared, respectively. Similarly, the driving force behind the Landé magnetic-fieldcontribution, being independent of lateral dimensions, is the difference in electrong factors between the two material constituents. We note that, for InAs/GaAs nanowiresuperlattices, it is possible to tune the effective barrier potential around 0 forcross-sectional dimensions of 5–6 nm by use of a magnetic field. Further, since the effectivebarrier potential is different for spin-up and spin-down polarized electrons, magnetic-fieldtuning can be used to separate spin-up and spin-down electrons in quantum-wiresuperlattices.