Optical Characterization of Buried Ingaas/GaAs Wires Overgrown by MBE

We have prepared buried InGaAs/GaAs wires by high resolution electron beam lithography, wet chemical etching and subsequent MBE overgrowth. Wires with lateral widths of less than 40nm have been realized. For optimized regrowth conditions such as growth temperature, growth rate, III/V ratio, and arsenic flux a smooth surface morphology of the 100nm thick overgrown (Al)GaAs layer is obtained. Etched only ultra narrow wires show a decrease of radiative recombination due to process induced defects and surface recombination at the open sidewalls. Optical investigations of narrow overgrown wires show a significant enhancement (up to two orders of magnitude) of the photoluminescence intensity. This is due to the disappearance of the open sidewalls and carrier capture from the overgrown barrier. o ]From studies of the influence of the crystallographic orientation on the quantum efficiency we find, that B surfaces of the wires offer the best conditions for MBE overgrowth.