Local Droplet Etching: Self-assembled Nanoholes for Quantum Dots and Nanopillars

Abstract

We review the mechanism and recent applications of the self-organized patterning of semiconductor surfaces by local droplet etching (LDE). LDE is a nanofabrication technique that is applicable in situ during molecular beam epitaxy (MBE) and fully compatible with state-of-the-art MBE systems. Most importantly, as a local etching technique that works with a number of different materials, it adds a new degree of freedom to established self-assembling techniques. During LDE, metallic droplets drill nanoholes into a semiconductor surface with structural parameters adjustable over a wide range by the process conditions. In subsequent overgrowth steps the holes are filled for the formation of nanostructures like, e.g., quantum dots (QDs)Quantum dots or quantum pillars. In comparison to other QD systems, the LDE dots have the key advantages that they are strain-free, highly uniform, and that their size is precisely adjustable. In addition, vertically stacked quantum dot molecules have been realized. Crystalline nanopillars are created by a combination of in situ LDE with ex situ selective etching that are highly attractive for studies of ballistic phonon and electron transport, e.g., in the field of thermoelectrics.