The fundamental understanding of quantum dot (QD) growth mechanism is essential to improve QD based optoelectronic devices. The size, shape, composition, and density of the QDs strongly influence the optoelectronic properties of the QDs. In this article, we present a detailed review on atomic-scale characterization of droplet epitaxy quantum dots by cross-sectional scanning tunneling microscopy (X-STM) and atom probe tomography (APT). We will discuss both strain-free GaAs/AlGaAs QDs and strained InAs/InP QDs grown by droplet epitaxy. The effects of various growth conditions on morphology and composition are presented. The efficiency of methods such as flushing technique is shown by comparing with conventional droplet epitaxy QDs to further gain control over QD height. A detailed characterization of etch pits in both QD systems is provided by X-STM and APT. This review presents an overview of detailed structural and compositional analysis that have assisted in improving the fabrication of QD based optoelectronic devices grown by droplet epitaxy.
Keywords: atom probe tomography; cross-sectional scanning tunneling microscopy; droplet epitaxy; optoelectronics; quantum dots.