Stark Spectroscopy and Radiative Lifetimes in Single Self-Assembled CdTe Quantum Dots

TL;DR

This study investigates Coulomb interactions and wave function modifications in single CdTe quantum dots, revealing that holes are more susceptible to charge state changes than electrons, with implications for quantum dot optical properties.

Contribution

It provides new insights into hole wave function softness and Coulomb correlation effects in self-assembled CdTe quantum dots, supported by Stark shift and lifetime measurements.

Findings

Hole wave function is more easily modified than electron wave function.

Lifetimes are shorter than expected for strong confinement.

Universal spectroscopic shift sequence due to Coulomb correlations.

Abstract

We present studies on Coulomb interactions in single self-assembled CdTe quantum dots. We use a field effect structure to tune the charge state of the dot and investigate the impact of the charge state on carrier wave functions. The analysis of the quantum confined Stark shifts of four excitonic complexes allows us to conclude that the hole wave function is softer than electron wave function, i. e. it is subject to stronger modifications upon changing of the dot charge state. These conclusions are corroborated by time-resolved photoluminescence studies of recombination lifetimes of different excitonic complexes. We find that the lifetimes are notably shorter than expected for strong confinement and result from a relatively shallow potential in the valence band. This weak confinement facilitates strong hole wave function redistributions. We analyze spectroscopic shifts of the observed excitonic complexes and find the same sequence of transitions for all studied dots. We conclude that the universality of spectroscopic shifts is due to the role of Coulomb correlations stemming from strong configuration mixing in the valence band.