Exciton properties and optical response inInxGa1−xAs/GaAs strained quantum wells

Exciton binding energies and optical response in quantum wells and in multiple quantum wells of GaAs/${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs are computed by a variational envelope-function procedure using the four-band model and the simpler two-band model. The effect of hydrostatic and uniaxial strain are considered from a virtual-crystal stress Hamiltonian. The physical parameters used for the alloy (${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As) are obtained by interpolating the parameter values of pure materials (GaAs, InAs). We verify that band-offset values in the range of 0.30–0.45 give exciton states and optical response in good agreement with experiments. The light-hole exciton energy is also well reproduced by theory and results are very close to the continuum states of the well, its binding energy being due to the attraction of the electron, localized inside the well.