Photoelectron generation and capture in the resonance fluorescence of a quantum dot

TL;DR

This study uses time-resolved resonance fluorescence to analyze how free charge carriers are generated and captured in a quantum dot, revealing that even resonant excitation produces free electrons that affect optical properties.

Contribution

It provides direct observation of electron capture and tunneling in a quantum dot under resonant excitation, highlighting a previously neglected detrimental effect.

Findings

Electrons are captured into the quantum dot during resonance fluorescence.

Captured electrons tunnel out on the order of milliseconds.

Free electrons generated can negatively impact quantum dot optical properties.

Abstract

Time-resolved resonance fluorescence (RF) on a single self-assembled quantum dot (QD) is used to analyze the generation and capture of photoinduced free charge carriers. We directly observe the capture of electrons into the QD in an intensity reduction of the exciton transition. The exciton transition is quenched until the captured electron tunnels out of the dot again in the order of milliseconds. Our results demonstrate that even under resonant excitation, excited, free electrons are generated, which can negatively influence the optical properties of a QD. This detrimental effect has been neglected before for dots that are optimized for maximum efficiency and minimum spectral diffusion.