Optical characterization of GaAs/AlGaAs nanostructures fabricated by focussed laser beam induced thermal interdiffusion

A novel technique is presented to modulate the effective band gap of GaAl/AlGaAs quantum well structures. Al/Ga interdiffusion on a lateral scale of about 100 nm is achieved by heating the sample locally with a focussed laser beam. Rapid thermal interdiffusion is limited to a small region underneath the laser spot center. Various lateral nanostructures have been fabricated by stepping the sample below the focussed laser beam. Wire structures with periods of about 200 nm reveal a significant peak structure and a blue shift of the photoluminescence. The strong photoluminescence efficiency allows microscopic optical characterization even of single quantum wire structures.