Droplet epitaxy of GaAs quantum dots on (0 0 1), vicinal (0 0 1), (1 1 0), and (3 1 1)A GaAs

Abstract

We study the formation of GaAs quantum dots (QDs) by droplet epitaxy on various GaAs surfaces. The fabrication process consists of two steps. First, liquid Ga droplets are grown in a Volmer-Weber-like mode. This is followed by crystallization under As pressure. We demonstrate fabrication of droplet epitaxial GaAs QDs on (0 0 1), vicinal (0 0 1), (1 1 0), and (3 1 1)A GaAs surfaces. On (3 1 1)A GaAs, QDs are formed with higher density and smaller height compared to (0 0 1) and (1 1 0), which is attributed to a higher energy barrier for surface diffusion. Values of the surface diffusion barrier are determined and its influence on temperature-dependent QD density is studied by means of a QD growth model. On vicinal (0 0 1) surfaces, step bunches are found to act as preferred nucleation sites for GaAs QDs which opens the possibility for a lateral positioning of the QDs by pre-patterning.