FINITE-SIZE EFFECTS IN ONE-DIMENSIONAL STRAINED SEMICONDUCTOR HETEROSTRUCTURES

The elastic lattice deformation of strained one-dimensional (1D) semic onductor heterostructures (quantum wires) is investigated theoreticall y. We consider the case of lattice-mismatched [100]-oriented superlatt ices made of cubic symmetry materials with a finite lateral dimension along the [011]- or the [001]-crystallographic direction. Due to the s mall lateral dimension of the quantum wires, an elastic stress relaxat ion occurs near the free surfaces. The theoretical evaluation of strai n fields in these 1D heterostructures is made with a Fourier series tr eatment and by using the elasticity theory and the condition of zero t otal stress on the free surfaces. We also investigate the effect of st rain on the confinement potentials. In the case of 1D heterostructures made by materials with zinc-blende symmetry, the nonuniform lattice d eformations can induce polarization charges due to the piezoelectric e ffect. Large band-gap and valence-band-splitting energy modulations of several tens of meV can be obtained near the free surfaces, inducing strong variations in the confinement potentials, which could cause red -shifted electron-hole transitions. Our analytical expressions for the nonuniform strain and stress fields, piezoelectric fields, and confin ement potentials are valid for any zinc-blende heterostructure made of III-V and II-VI semiconductor compounds. Our results clearly demonstr ate that, in addition to the 1D confinement that is caused by the redu ced geometrical lateral dimension, the elastic strain relaxation and t he piezoelectric fields on the free surfaces of the quantum wires must be considered in order to understand and describe correctly the elect ronic properties of 1D heterostructures.