Abstract
We present an experimental study on the optical quality of InAs/InP quantum dots (QDs). Investigated structures have application relevance due to emission in the 3rd telecommunication window. The nanostructures are grown by ripening-assisted molecular beam epitaxy. This leads to their unique properties, i.e., low spatial density and in-plane shape symmetry. These are advantageous for non-classical light generation for quantum technologies applications. As a measure of the internal quantum efficiency, the discrepancy between calculated and experimentally determined photon extraction efficiency is used. The investigated nanostructures exhibit close to ideal emission efficiency proving their high structural quality. The thermal stability of emission is investigated by means of microphotoluminescence. This allows to determine the maximal operation temperature of the device and reveal the main emission quenching channels. Emission quenching is predominantly caused by the transition of holes and electrons to higher QD’s levels. Additionally, these carriers could further leave the confinement potential via the dense ladder of QD states. Single QD emission is observed up to temperatures of about 100 K, comparable to the best results obtained for epitaxial QDs in this spectral range. The fundamental limit for the emission rate is the excitation radiative lifetime, which spreads from below 0.5 to almost 1.9 ns (GHz operation) without any clear spectral dispersion. Furthermore, carrier dynamics is also determined using time-correlated single-photon counting.
Highlights
Licensee MDPI, Basel, Switzerland.Developing efficient non-classical light sources operating at room temperature and compatible with telecommunication windows is the holy grail of quantum communication and quantum information processing [1,2,3,4,5,6,7,8]
For extraction efficiency and carrier dynamics measurements, a setup based on a NbN superconducting nanowire single-photon detector (SSPD), optimized for telecom wavelengths with quantum efficiency exceeding 80% and time jitter below 50 ps, and less than 100 dark counts/s at 1550 nm, was utilized
The number of photons collected by the first lens in the optical setup per second is divided by the repetition rate of the excitation laser
Summary
Epitaxial QDs hold performance records in this regards [1,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38] These are inherently quantum emitters (with non-classical emission statistics) that have been proven to constitute nearly ideal single-photon sources at emission wavelengths below 1 μm [4,8,38,39,40].
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