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February, 2017

The ability to generate on-demand single-photons is of vital importance to quantum information technology such as quantum cryptography, linear optical quantum computing and quantum metrology. Due to their high stability, good repetition rates, and practicable incorporation into cavities and electrically pumped structures, quantum dots (QDs) are ideal candidates for the generation of, and interaction with, single photons. Notably nitride QDs offer the advantages of large exciton binding energies and large band offsets which allow higher temperature operation. InGaN QDs, in particular, have some attractive properties for quantum information systems, such as access to the blue spectral range which is both ideally suited to sattelite-based communications and well-matched to efficient and practical fast single-photon detectors.  However, QDs grown on the polar c-plane experience large internal electric fields leading to slow single-photon emission rates and unpolarized emission which limit their applicability to quantum information systems.

Here, we demonstrate single-photon emission from InGaN QDs grown on an alternative, non-polar crystal plane.  The QDs are embedded on the m-plane side-walls of GaN nanowires. The QD exhibits single photon emission up to 100 K. Studies on a statistically significant number of QDs show that these m-plane QDs exhibit very short radiative lifetimes (~260 ps) which would allow high repetition rates in a quantum information system. Moreover, the observed single photons are almost completely linearly polarized perpendicular to the crystallographic c-axis. Such InGaN QDs incorporated in a nanowire system meet many of the requirements for implementation into quantum information systems and could potentially open the door to wholly new device concepts.

Figure. Schematic illustration of self-assembled InGaN QDs-in-nanowire grown by metal-organic vapour phase epitaxy. These QDs exhibit many advantageous properties, such as significantly anti-bunched emission up to 100 K, a strong degree of linear polarisation, and very fast radiative lifetimes.

T. J. Puchtler, T. Wang, C. X. Ren, F. Tang, R. A. Oliver, R. A. Taylor, and T. Zhu, “Ultrafast, Polarized, Single-Photon Emission from m-Plane InGaN Quantum Dots on GaN Nanowires”, Nano Letters 16(12) (2016) pp. 7779–7785

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