Two-Dimensional Array of Self-Assembled AlInAs Quantum Wires

We present the optical and structural characterization of a two-dimensional array of self-organized AlInAs quantum wires. The structure was created by epitaxially stacking along the [001] direction thin self-assembled, [100]-oriented, superlattices separated by homogeneous layers of Al _0.48In_0.52As. Vertical and lateral self-alignment results in a highly regular array of wires oriented along the [010] direction. The wire cross-sectional dimensions are about 10×14.4nm² and their density is 1.9×10¹¹cm^-2. The energy and the nature of the electronic transitions are significantly affected by confinement in two dimensions: (1) a blueshift of about 100 meV is observed and (2) the two lowest energy transitions are both polarized along the [010] direction. For comparison, the two lowest energy transitions of a lateral superlattice with similar characteristics have a heavy- (polarization along [010]) and a light-hole character (polarization along [100]). Large polarization ratios are measured for both transitions.