A comprehensive theoretical study of the effects of in-plane uniaxial stress on the excitonic absorption spectra of GaAs/Al1-xGax As quantum wells is presented. In particular, stress is used to investigate optical features of excitonic mixing effects. State-of-the-art calculations of realistic excitonic absorption spectra under stress are performed that take valence-band mixing and the stress-induced anisotropy of the band structure into account. Two important aspects of in-plane uniaxial stress are identified each of which affects exciton mixing in a different way. On the one hand, the natural quantization direction gets rotated by stress from the confinement direction to the stress direction. This leads to a marked polarization dependence of the absorption spectrum, which can be explained within a simple model of single-particle zone-center states. On the other hand, uniaxial stress also allows the energy alignments of the valence states to be varied substantially. Thereby it is possible to influence the k · P-related exciton mixing considerably, in particular between the lowest 1s light-hole exciton and the p continuum of the second heavy-hole exciton. This leads to the formation of doublet structures that reveal strong anticrossing behavior and have peculiar properties, which are best described within the framework of the Fano-Anderson model. Excellent agreement was achieved up to large stress values between our theoretical results and our experimental photoreflectance and photoluminescence results, with respect to the polarization dependence of the transition intensities and the stress dependence of the exciton energies. This clearly demonstrates the high accuracy of the calculations and provides conclusive evidence for the strong mixing effects that stress can cause.
|Original language||English (US)|
|Number of pages||15|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jan 1 1999|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics