Solid-state single and entangled photon emitters linked coherently over long distances with optical fibers enable a new generation of quantum-based communications networks. Currently, epitaxial semiconductor quantum dots (QDs) pave the way as a scalable approach for fabricating deterministic non-classical light sources that can be integrated with other photonic or electronic components in miniaturized form. Here, we present a new quantum material system based on GaSb QDs formed by filling droplet-etched nanoholes [1,2], a technique which has been previously used for the state-of-the-art single- and entangled-photon sources in the GaAs-based materials emitting at wavelengths shorter than 800 nm [3-6]. We show that while the GaSb QDs exhibit high homogeneity and small fine structure splitting similarly to their GaAs counterparts, they also enable single-photon emission in the 3rd telecom window [7] with prospects for extending towards 2µm. These properties make them ideal candidates for quantum photonic applications requiring compatibility with Si-photonics and fiber-based telecom.
[1] J. Hilska et al. Cryst. Growth Des. 21 1917−1923, 2021
[2] A. Chellu et al. APL Materials 9, pp
Advances in single-photon sources have proved pivotal to the progress of quantum information processing and secure communication systems. This study addresses the imperative need for developing commercially viable, electrically-driven single-photon sources capable of operating at or above room temperature with rapid response times and emission in the telecom wavelength range of 1260 to 1675 nm. We introduce an innovative single-photon light-emitting diode (SPLED) design employing GaAs quantum dots (QDs) and self-assembled GaSb quantum rings (QRs). The core of our design is an electron filter layer composed of GaAs QDs embedded in AlxGa1-xAs, engineered to inject (single) electrons into an ensemble of type-II GaSb QRs in GaAs, where they recombine with strongly confined holes producing (single) photons at a wavelength governed by an optical cavity created using distributed Bragg reflectors (DBRs). This concept removes the need to select individual QD emitters, rendering the device highly suitable for scalable production. Our research demonstrates a comprehensive theoretical and experimental analysis using nextnano++ simulations and fabricated prototype device characteristics. Quite remarkably, we find that the emission properties of the SPLED devices actually improves as operational temperature is increased from 20 °C to 80 °C, making them attractive as practical devices.
This research focuses on strain-free GaSb/AlGaSb quantum dots (QDs) grown via local droplet etching (LDE) for their potential in quantum photonic applications. These QDs exhibit excitonic emission in the telecom S-band with a narrow ensemble emission linewidth. Through theoretical modeling in addition to previous photoluminescence experiments, the study investigates the electronic band structure, dipole transitions, and dimensions of the GaSb/AlGaSb QDs. Key findings include insights into the indirect-direct bandgap crossover based on QD dimensions and the comparison of dipole transitions with photoluminescence measurements. The results contribute to the practical integration of these QDs in quantum photonic devices and fiber optics-based quantum key distribution networks.
As a type-II heterostructure with exclusive hole confinement GaSb/(Al,Ga)As QDs are an ideal candidate for
a QD based memory device operating at room temperature. We investigated different Antimony-based QDs in
respect of localization energies and storage times with 8-band-k•p calculations as well as time-resolved capacitance
spectroscopy. In addition, we present a memory concept based on self-organized quantum dots (QDs) which could
fuse the advantages of today's main semiconductor memories DRAM and Flash. First results on the performance
of such a memory cell are shown and a closer look at Sb-based QDs as a storage unit is taken.
Efficient generation of polarized single or entangled photons is a crucial requirement for the implementation
of quantum key distribution (QKD) systems. Self-organized semiconductor quantum dots (QDs) are capable of
emitting one polarized photon or an entangled photon pair at a time using appropriate electrical current injection.
We realized highly efficient single photon sources (SPS) based on well established semiconductor technology: In
a pin structure a single electron and a single hole are funneled into a single InAs quantum dot using a submicron
AlOx current aperture. Efficient radiative recombination leads to emission of single polarized photons with an
all-time record purity of the spectrum. Non-classicality of the emitted light without using additional spectral
filtering is demonstrated. Out-coupling efficiency and emission rate are increased by embedding the SPS into a
micro-cavity of Q = 140. The design of the micro-cavity is based on detailed modeling to optimize its performance.
The resulting resonant single-QD diode generates single polarized photons at a repetition rate of 1 GHz exhibiting
a second order correlation function of g(2)(0) = 0.
Eventually, QDs grown on (111) oriented substrate are proposed as source of entangled photon pairs. Intrinsic
symmetry-lowering effects leading to the splitting of the exciton bright states are shown to be absent for this
substrate orientation. As a result the XX → X → 0 recombination cascade of a QD can be used for the generation
of entangled photons without further tuning of the finestructure splitting via QD size and/or shape. We present
first micro-photoluminescence studies on QDs grown on (111) GaAs, demonstrating a fine structure splitting less
than the spectral resolution of our set-up.
Interaction between strongly localized charge carriers in zero-dimensional systems like quantum dots (QD) depends sensitively on the geometrical roperties of the dots. The recently observed monolayer splitting with eight well resolved peaks (in low excitation photoluminescence (PL)) together with eight-band kp theory as the appropriate tool for modeling electronic and optical properties offers direct spectroscopic access to details of the QD morphology. By this achievement it became possible to link single-dot spectra obtained by cathodoluminescence measurements via the exciton transition energy to structural properties of the probed QD. In view of theory this situation constitutes an ideal starting point to study few-particle interactions for realistic InAs QDs as a function of their structural properties. This is done using the configuration interaction method. The wavefunctions are obtained from eight-band kp calculations of single-particle states including explicitly piezoelectric effects in the confinement potential.
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