Complex optical signatures from quantum dot nanostructures and behavior in inverted pyramidal recesses

A study of previously overlooked structural and optical properties of InGaAs heterostructures grown on (111)B oriented GaAs substrates patterned with inverted 7.5-μm pitch pyramidal recesses is presented. First, the composition of the confinement barrier material (GaAs in this work) and its growth temperature are shown as some of the key parameters that determine the main quantum dot properties, including nontrivial emission energy dependence, excitonic pattern, and unusual photoluminescence energetic ordering of the InGaAs ensemble nanostructures. Second, the formation of a formerly unidentified type of InGaAs nanostructures - three corner quantum dots - is demonstrated in our structures next to the well-known ones (a quantum dot and three lateral quantum wires and quantum wells). The findings show the complexity of the pyramidal quantum dot system which strongly depends on the sample design and which should be considered when selecting highly symmetric (central) quantum dots in newly designed experimental projects.