Strain‐Free GaSb Quantum Dots as Single‐Photon Sources in the Telecom S‐Band

Generating single photons in the telecommunication wavelength range from semiconductor quantum dots (QDs) and interfacing them with spins of electrons or holes is of high interest in recent years, with research mainly focusing on indium‐based QDs. However, there is not much data on the optical and spin properties of gallium antimonide (GaSb) QDs, despite it being a physically rich system with an indirect to direct bandgap crossover in the telecom wavelength range. This work investigates the (quantum‐) optical properties of GaSb QDs, which are fabricated by filling droplet‐etched nanoholes in an aluminum gallium antimonide (AlGaSb) matrix. Photoluminescence (PL) features from isolated and highly symmetric QDs are observed that exhibit narrow linewidth in the telecom S‐band and show an excitonic fine structure splitting of up to ΔEFSS=(12.0±0.5)$\mathrm{\Delta}{\mathrm{E}}_{\mathrm{FSS}}= (12.0 \pm 0.5)$ µeV. Moreover, time‐resolved measurements of the decay characteristics of an exciton are performed and the second‐order photon autocorrelation function of the charge complex is measured to g2(0)=0.16±0.02${{\mathrm{g}}}^{\mathrm{2}}{\mathrm{(0)}} = 0.16 \pm 0.02$, revealing clear antibunching and thus proving the capability of this material platform to generate non‐classical light. Strain‐free gallium‐antimonide quantum dots are fabricated via local droplet etching and subsequent nanohole infilling and investigated for their (quantum‐) optical properties. Time‐resolved photoluminescence and second‐order autocorrelation measurements are conducted on an excitonic transition, showcasing antibunching and thereby highlighting the material platform's potential as a resource for generating non‐classical light in the telecom range.