Optical properties of stepped InxGa1-xAs/GaAs quantum wells

A systematic study of InxGa1-xAs/InyGa1-yAs/GaAs(001) stepped quantum wells with indium composition x = 14.9% and y = 6.4% and thicknesses in the range of quasi-two-dimensional behaviour of Wannier excitons is performed. Optical spectra are compared with model calculations obtained by an accurate exciton envelope function. We point out that optical spectroscopy is a tool for studying indium diffusion in stepped wells, and this property is crucial in order to obtain second harmonic generation enhanced with respect to the bulk value.