Structure and optical properties of semiconductor quantum nanostructures self-formed in inverted tetrahedral pyramids

We present a method for fabricating quantum dots using seeded self-organize d growth of GaAs/AlGaAs heterostructures on substrates patterned with inver ted pyramids. This method produces, at the tip of each inverted pyramid, hi ghly uniform quantum dots whose size and position can be accurately control led. In addition, a system of connected GaAs and AlGaAs two- and one-dimens ional nanostructures is identified in the inverted pyramids using cross-sec tional atomic force microscopy. A substrate removal technique is used to op timally prepare our samples for optical studies, allowing the increase of t he luminescence efficiency of the quantum dots by up to three orders of mag nitude. Micro-photoluminescence and cathodo-luminescence spectroscopy are u sed to study in detail the bandgap structure of the connected nanostructure s identified in the pyramids, which constitute a complex, bur controlled, b arrier environment for the quantum dots.