HOLE-SUBBAND-ORDER REVERSAL IN GAAS/INXAL1-XAS STRAINED-LAYER SUPERLATTICES INVESTIGATED BY PHOTOREFLECTANCE SPECTROSCOPY

We have measured photoreflectance (PR) spectra of the exciton transitions associated with the n=1 electron and hole subbands in GaAs (dG) In0.2Al0.8As(dI) strained-layer superlattices with dG=dI of 10, 40, and 100 Å and a GaAs (100 Å)/AlAs (100 Å) superlattice to investigate the hole-subband order. The PR-intensity profiles of the heavy-hole and light-hole excitons demonstrate that the order of the n=1 heavy-hole and light-hole subbands is changed by the In concentration (strain effects) and the layer thickness (quantum-size effects). We have analyzed the experimental results according to an effective-mass approximation including strain effects. © 1992.