Atomically precise quantum dots fabricated by two-fold cleaved edge overgrowth: from artificial atoms to molecules

Abstract

The optical properties of different quantum dot structures consisting of individual dots, pairs of coupled dots as well as of linear arrays of dots have been studied experimentally. The 7×7×7 nm 3 size GaAs quantum dots form at the intersection of three orthogonal quantum wells fabricated by two-fold application of the cleaved edge overgrowth method. The high degree of control over shape, composition and position of the dots, achievable by this technique, allows a detailed investigation of the influence of coupling between almost identical zero-dimensional objects. In this way an “artifical molecule”, characterized by the existence of bonding and antibonding states, can be assembled from two of such “artificial atoms”. The coupling strength between the “artificial atoms” directly adjusts the “interatomic” distance and is reflected in the energetic separation of the bonding and antibonding levels and the line widths of the corresponding interband transitions observed by means of microscopic photoluminescence spectroscopy.