Optical properties of free-standing GaAs semiconductor nanowires and their dependence on the growth direction

The electronic states of a free-standing widegap semiconductor quantum nanowire are investigated. We applied the variational technique using the effective mass approximation within the k·p model to a thin cylindrical GaAs nanowire. The energy dispersion, the distribution of the spinor components, and the optical absorption spectra are presented. The hole dispersion shows a typical ``camel back'' structure. The effect of the dielectric mismatch between the wire and the surrounding medium and the influence of the growth direction of the wire are examined. We find that the photoluminescence energy of the exciton is larger in the [001] configuration than the [111] configuration.