Speaker
Description
The promising application of single-photon sources (SPS) in quantum communication and cryptography has driven significant advances in this field and the search for new active materials. Among various emitters, semiconductor quantum dots (QDs) are of particular interest due to their high-quality single-photon emission, high generation rates, low multi-photon emission probabilities, and compatibility with semiconductor technologies [1]. However, only QDs emitting below 1 µm have reached near-ideal SPS status. GaAs/AlGaAs QDs grown via nanohole droplet etching epitaxy are notable examples, allowing precise control over size, resulting in high uniformity [2]. For fiber-optic communication, emission in the 3rd telecommunication window is essential, which drives interest in antimony-based and InP-based material systems.
This work explores (In)GaSb QDs epitaxially grown by filling nanoholes etched with GaSb droplets in an AlGaSb matrix [3]. Unlike other antimony-based QDs, such as InSb/InAs and GaSb/GaAs, InGaSb/AlGaSb QDs exhibit a type-I band alignment and narrow emission near 1.55 μm, making them promising telecom SPS [4,5]. We performed optical characterization on samples with varying In compositions, tuning emission between the S, C, and L bands of the 3rd telecommunication window. Techniques such as photoluminescence excitation, power- and temperature-dependent photoluminescence were used to determine emission wavelengths, uniformity, and excitonic properties, providing insight into optimizing QD performance and understanding photoluminescence quenching and spectral tunability.
Additionally, we conducted theoretical modeling using the multi-band k·p method, which includes strain, piezoelectric fields, and spin-orbit coupling [6]. We developed a realistic 3D model of the QDs based on structural data (3D atomic force microscopy scans of surface nanoholes after etching and after filling with QD material) to predict electronic and optical properties. Excitonic effects are included using the configuration interaction method. These theoretical predictions are crucial for interpreting optical spectra, guiding further quantum dot optimization.
This work was financed by FiGAnti project funded within the QuantERA II Programme that has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 101017733 and National Science Centre, Poland- project 2023/05/Y/ST3/00125.
[1] X. Zhou, L. Zhai, and J. Liu, Photonics Insights 1, R07 (2022).
[2] S. Covre da Silva et al., Appl. Phys. Lett. 119, 120502 (2021).
[3] J. Hilska, A. Chellu, and T. Hakkarainen, Crystal Growth & Design 21, 1917 (2021).
[4] A. Chellu et al., Appl. Phys. Lett. Mater. 9, 051116 (2021).
[5] J. Michl et al., Adv. Quantum Technol. 6, 2300180 (2023).
[6] K. Gawarecki, Phys. Rev. B 97, 235408 (2018).
