Charge tuning in [111] grown GaAs droplet quantum dots

TL;DR

This paper demonstrates charge tuning in strain-free GaAs/AlGaAs quantum dots grown by droplet epitaxy, revealing excited states and magnetic properties through micro-photoluminescence at cryogenic temperatures.

Contribution

It introduces controlled charge tuning in droplet-grown GaAs quantum dots and uncovers excited valence and conduction states with magnetic field effects.

Findings

Charge tuning from -3|e| to +2|e| in GaAs QDs.

Observation of excited valence and conduction states.

Negative diamagnetic shift in excited charged excitons.

Abstract

We demonstrate charge tuning in strain free GaAs/AlGaAs quantum dots (QDs) grown by droplet epitaxy on a GaAs(111)A substrate. Application of a bias voltage allows the controlled charging of the QDs from $-3|e|$ to $+2|e|$. The resulting changes in QD emission energy and exciton fine-structure are recorded in micro-photoluminescence experiments at T=4K. We uncover the existence of excited valence and conduction states, in addition to the s-shell-like ground state. We record a second series of emission lines about 25meV above the charged exciton emission coming from excited charged excitons. For these excited interband transitions a negative diamagnetic shift of large amplitude is uncovered in longitudinal magnetic fields.