Spin properties in droplet epitaxy-grown telecom quantum dots

TL;DR

This study demonstrates that droplet epitaxy-grown InAs/InGaAs/InP quantum dots emit in the telecom band and exhibit significantly improved spin properties, including longer spin relaxation times and reduced g-factor anisotropy, making them promising for quantum information.

Contribution

The paper introduces a novel growth method using droplet epitaxy for telecom quantum dots, resulting in enhanced spin coherence and structural symmetry compared to traditional growth techniques.

Findings

Electron g-factor of 0.934 measured

Spin relaxation time of 2.95 microseconds achieved

Reduced g-factor anisotropy observed

Abstract

We investigate the spin properties of InAs/InGaAs/InP quantum dots grown by metalorganic vapor-phase epitaxy (MOVPE) deposition using droplet epitaxy, which emit in the telecom C-band. Using pump-probe Faraday ellipticity measurements, we determine electron and hole $g$-factors of $|g_e| = 0.934$ and $|g_h| = 0.471$, with the electron $g$-factor being nearly twice as low as typical molecular beam epitaxy Stranski-Krastanov (SK) grown samples. Most significantly, we measure a longitudinal spin relaxation time $T_1 = 2.95\,\mu s$, representing an order of magnitude improvement over comparable MBE SK grown samples. Despite significant electron $g$-factor anisotropy, we observed that it is reduced relative to similar material composition samples grown with MBE or MOVPE SK methods. We attribute these g-factor anisotropy and spin lifetime improvements to the enhanced structural symmetry achieved via MOVPE droplet epitaxy, which mitigates the inherent structural asymmetry in strain-driven growth approaches for InAs/InP quantum dots. These results demonstrate that MOVPE droplet epitaxy-grown InAs/InGaAs/InP quantum dots exhibit favorable spin properties for potential implementation in quantum information applications.