Excitons in CdTe quantum wires with strain-induced lateral confinement

Using a two-step epitaxial growth process we have fabricated nanometer-scale quantum wires through the modulation of the in-plane lattice constant of a [110] CdTe/${\mathrm{Cd}}_{\mathit{x}}$ ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$Te quantum well grown on top of a [001] CdTe/${\mathrm{Cd}}_{\mathit{x}}$ ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$Te strained superlattice. With respect to the unmodulated [110] quantum well, the photoluminescence of these quantum wires presents a large redshift which depends strongly on the excitation density. The results compare very well with a theoretical model assuming no strain relaxation in the structure. In this framework, we show that (i) the hole is confined via the Coulomb attraction of the electron and not via the valence-band offset, and (ii) due to the nonlinearity of the piezoelectric coefficient in CdTe, a lateral piezoelectric field is present in these strained modulated [110] wires. © 1996 The American Physical Society.