Surface quantum dots with pure, coherent, and blinking-free single photon emission

TL;DR

This paper demonstrates that quantum dots grown directly on semiconductor surfaces can emit pure, coherent, and stable single photons without blinking, after sulphur passivation, enabling advanced quantum nano-devices.

Contribution

The study shows complete optical property restoration of surface-grown quantum dots through sulphur passivation, overcoming previous limitations of weak and unstable emissions near surfaces.

Findings

Single photons with 98.8% purity and 77% indistinguishability.

Linewidths down to 4 μeV and 99.69% persistency.

Stable emission over two years and after nanomanufacturing.

Abstract

The surface of semiconductor nanostructures has a major impact on their electronic and optical properties. Disorder and defects in the surface layer typically cause degradation of charge carrier transport and radiative recombination dynamics. However, surface vicinity is inevitable for many scalable nano-optical applications. Epitaxially grown quantum dots are the best candidate for high-performance single photon emission and show great potential for quantum technologies. Yet, these emitters only reveal their excellent properties if they are deeply embedded in a semiconductor host. Until today, quantum dots close to surfaces yield weak, broad, and unstable emissions. Here, we show the complete restoration of optical properties from quantum dots grown directly on a semiconductor surface. The vanishing luminescence from the as-grown sample turns into bright, ultra-stable, coherent and blinking-free single photon emission after sulphur passivation. Under quasi-resonant excitation, single photons are generated with 98.8% purity, 77% indistinguishability, linewidths down to 4 $\mu$eV and 99.69% persistency across 11 orders of magnitude in time. The emission is stable even after two years and when being subjected to nanomanufacturing processes. Some long-standing stumbling blocks for surface-dominated quantum dots are thereby removed, unveiling new possibilities for hybrid nano-devices and applications in quantum communication or sensing.