Lateral quantization effects in the optical properties of barrier modulated InGaAs/GaAs wires

Abstract
We have studied the optical properties of barrier modulated InGaAs/GaAs quantum wires with widths down to about 20 nm. Here the lateral confinement is introduced via the change of the band discontinuity due to the modulation of the upper barrier of a quantum well structure. For wire widths below 50 nm the emission spectra shift systematically to higher energy which is associated to the lateral confinement. Using the geometrical wire widths measured by scanning electron microscopy the width dependence of the emission can be calculated in good agreement with the experimental data. In photoluminescence excitation experiments up to three transitions which arise from lateral confined states can be observed. For the smallest wires we observe a broadening of the emission spectra which can be explained in terms of size fluctuation. The barrier modulated wires show a strong linear polarization of the emission parallel to the wire axis up to about 25 % for 20 nm wide wires.