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 0.027 m/sub 0/ 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/Al/sub 0.4/Ga/sub 0.6/As QWS with a 50 A*50 AA cross section. This value is six times larger than that in the 50-AA quantum well. With an electric field of 8*10/sup 4/ V/cm perpendicular to the heterointerface, a maximum refractive index change 30% larger than this value is estimated.<
>