BAND-MIXING EFFECTS AND EXCITONIC OPTICAL-PROPERTIES IN GAAS QUANTUM WIRE STRUCTURES - COMPARISON WITH THE QUANTUM WELLS

The excitonic properties in quantum-wire structures (QWS) are analyzed by taking into account the band-mixing effects in the valence band of the structure. The effective mass value in the wire direction at the zone center of the lowest heavy-hole-like subband is found to be as small as 0.027m0 for GaAs/AlGaAs QWS. This reduced effective mass and the related nonparabolicity of the subband structure play a significant role in determining the exciton properties. Using these results, the maximum excitonic contribution to the refractive index value is estimated to be 0.59, i.e., 17.4% of the bulk value for a GaAs/Al0.4Ga0.6As QWS with a 50 angstrom × 50 angstrom cross section. This value is six times larger than that in the 50-angstrom quantum well. With an electric field of 8 × 104 V/cm perpendicular to the heterointerface, a maximum refractive index change 30% larger than this value is estimated.