Uniaxial stress dependence of spatially confined excitons.

Abstract

We report the first observation of the effect of two-dimensional (2D) confinement on the uniaxial stress dependence of excitons in GaAs/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As quantum wells. For uniaxial stress X\ensuremath{\parallel}[100], perpendicular to the quantization axis (z^\ensuremath{\parallel}[001]) of the exciton Hamiltonian without external stress, the exciton energy consists of two components. The first, containing hydrostatic strain terms, is the same for bulk and 2D excitons, in agreement, to within experimental error, with hydrostatic photoluminescence data. The second component contains shear strain terms and is observed to be dependent on quantum-well width. This dependence is interpreted in terms of a model based on the overlap of the light-hole (LH) and heavy-hole (HH) wave functions and on the energy differences between the LH and HH excitons.