PHOTOREFLECTANCE STUDY OF HOLE-SUBBAND STRUCTURES IN GAAS/INXAL1-XAS STRAINED-LAYER SUPERLATTICES

We have performed photoreflectance measurements of the exiton transitions associated with the first (n=1) subbands in GaAs(d(G) angstrom)/InxAl1-xAs(d(I) angstrom) strained-layer superlattices with (d(G), d(I) x) = (100, 100, 0) (100, 100, 0.1), (100, 100, 0.2), and (40, 40, 0.2) grown on (001) GaAs substrates. The photoreflectance-intensity profiles of the n = 1 excitons, which reflect the oscillator strength, clearly demonstrate that the order of the n = 1 \J = 3/2, m(J) = +/- 3/2 > (heavy-hole) subband and the n = 1 \3/2, +/-1/2> (light-hole) subband is changed by the In concentration (lattice-mismatch strain) and the layer thickness (quantum-size effect). We have analyzed the experimental results of the hole-subband order as a function of the In concentration and the layer thickness on the basis of an effective-mass approximation taking into account strain effects.