Enhanced sequential carrier capture into individual quantum dots and quantum posts controlled by surface acoustic waves

TL;DR

This paper demonstrates how surface acoustic waves can control carrier capture and exciton states in quantum dots and quantum posts, enhancing emission and enabling charge state switching.

Contribution

It introduces a method to manipulate exciton occupancy in quantum nanostructures using surface acoustic waves, revealing differences between quantum dots and quantum posts.

Findings

Switching of exciton charge states induced by surface acoustic waves

Continuous and hysteretic switching behaviors observed in quantum posts and dots

Enhanced emission intensity due to acoustically induced carrier trapping

Abstract

Individual self-assembled Quantum Dots and Quantum Posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For Quantum Posts, switching occurs continuously from predominantely charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent on whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is non-monotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which Quantum Dots nucleate. This limitation can be overcome for Quantum Posts where acoustically induced charge transport is highly efficient in a wide lateral Matrix-Quantum Well.