Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices

TL;DR

This study combines photoluminescence imaging and atomic force microscopy to locate and analyze InAs quantum dots relative to surface features, aiding the selection of optimal dots for quantum photonic devices.

Contribution

It introduces a combined optical and topographical characterization method to identify quantum dots near surface features without affecting their emission properties.

Findings

Quantum dots often appear near large surface features.

No significant spectral differences between dots near features and in defect-free regions.

Method applicable across multiple wafers and growth chambers.

Abstract

We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots (density <0.01 um^(-2) capped by a 95 nm GaAs layer, and emitting around 950 nm. By combining optical and scanning probe characterization techniques, we determine the position of single quantum dots with respect to comparatively large (100 nm to 1000 nm in-plane dimension) topographic features. We find that quantum dots often appear (>25% of the time) in the vicinity of these features, but generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions. This behavior is observed across multiple wafers produced in different growth chambers. Our characterization approach is relevant to applications in which single quantum dots are embedded within nanofabricated photonic devices, where such large surface features can affect the interaction with confined optical fields and the quality of the single-photon emission. In particular, we anticipate using this approach to screen quantum dots not only based on their optical properties, but also their surrounding surface topographies.