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Polarized single photon emission and photon bunching from an InGaN quantum dot on a GaN micropyramid
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-4547-6673
2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 6, 065702- p.Article in journal (Refereed) Published
Abstract [en]

We report on excitonic single photon emission and biexcitonic photon bunching from an InGaN quantum dot formed on the apex of a hexagonal GaN micropyramid. An approach to suppress uncorrelated emission from the pyramid base is proposed, a metal lm is demonstrated to eectively screen background emission and thereby signicantly enhance the signal-to-background ratio of the quantum dot emission. As a result, the second order coherence function at zero time delay g(2)(0) is signicantly reduced (to g(2)(0) = 0.24, raw value) for the excitonic autocorrelation at a temperature of 12 K under continuous wave excitation, and a dominating single photon emission is demonstrated to survive up to 50 K. The deterioration of the g(2)(0)-value at elevated temperatures is well understood as the combined eect of reduced signal-to-background ratio and limited time resolution of the setup. This result underlines the great potential of site controlled pyramidal dots as sources of fast polarized single photons.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015. Vol. 26, no 6, 065702- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-113347DOI: 10.1088/0957-4484/26/6/065702ISI: 000348448000018OAI: oai:DiVA.org:liu-113347DiVA: diva2:781478
Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Time Correlated Single Photon Spectroscopy on Pyramidal Quantum Dots
Open this publication in new window or tab >>Time Correlated Single Photon Spectroscopy on Pyramidal Quantum Dots
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Generation of non-classical light is both of fundamental interest and a common condition for quantum information applications (QIA). One feasible type of single photon emitter for QIA is based on semiconductor quantum dots (QDs), due to their atomic-like energy structure and their possibility to be integrated with other semiconductor devices on the same chip. Sitecontrolled QDs with highly linear polarized emission are a prerequisite for certain QIA and a close to room temperature operation is demanded for widespread applications.

III-nitride QD can have the deep connement potentials needed for high temperature operation, and the demonstration of single photon emission at room temperature was recently reported for a GaN QD [Nano Lett. 14, 982 (2014)]. Asymmetric III-nitride QD emits light with a high degree of linear polarization. To make site-controlled nitride-based QDs a promising approach is to deposit a thin layer of InGaN on top of hexagonal GaN micropyramids. QDs formed on the apex of the pyramids grown with this approach have been shown to exhibit single and sharp InGaN related emission lines with a high degree of linear polarization [Nano Lett. 11, 2415 (2011)]. A simple elongation of the pyramid base gives control of the polarization direction [Light: Sci. Appl. 3, e139 (2014)].

The work presented in this thesis deals with time correlation measurements, to measure, for the rst time, the single photon properties of these pyramidal QDs.

A time correlated single photon spectroscopy (TCSPS) setup was assembled, tested and used to perform measurements on these pyramidal QDs. The TCSPS apparatus measures the time dierences between subsequent photons emitted from the sample. In the spectrally ltered light of one emission line in the emission spectra, e.g. exciton emission, of a QD two or more photons cannot be emitted simultaneously, i.e. the photons are sent out one by one. A histogram of the ensemble of measured time dierences (~106 events) will then for the ideal case have no events for τ = 0, and very few for close to zero. This histogram, when normalized, is under certain conditions equal to the second order coherence function g(2)(τ ). In reality, however, there are photons coming from other sources close to the QD, i.e. background emission, that reach the detector and reduce the dip in the correlation histogram for small τ. There is also an statistical uncertainty in the measured time dierences and nally the nite bin width used in the histogram that deteriorate the measured correlation function. To understand the in uence on g(2)(τ) from background emission, instrument response function and the bin width, on the measurement on excitonic emission, simulations and calculations were made. The crucial variables were, for our samples and setup, the level of the background emission and the instrument response function.

A post growth process was developed to cover the lower parts of the pyramid sides as well as the area between the pyramids with a metal lm, to reduce the background emission. This reduces the background emission and largely improves the relative QD signal. As a result, signicant improved single photon characteristics were demonstrated.

A measurement of the second order coherence function for the excitonic autocorrelation at a temperature of 12 K, gave for zero time delay ( = 0) a value of g(2)(0) = 0.24 and the residual value of the second order coherence function (0.24) could be in full explained by the three variables, background emission, instrument response function and bin width. The g(2)(0) value for correlation measurements at higher temperatures of 50 K and 80 K is also fully explained by the three variables, showing that the emission from the QD itself is ideal up to 80 K.

This result underlines the great potential of these site controlled pyramidal dots as sources of fast polarized single photon emission, and provides the rst rigorous evidence of InGaN quantum dot formation on hexagonal GaN pyramids. We also show the rst proof of biexcitonic emission in this pyramidal QDs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 41 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1702
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113348 (URN)10.3384/lic.diva-113348 (DOI)978-91-7519-143-0 (ISBN)
Presentation
2015-01-30, Planck, Fysikhuset, Campus Valla, Linköpints universtet, Linköping, 14:15 (English)
Opponent
Supervisors
Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2016-06-07Bibliographically approved

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Jemsson, TomasMachhadani, HoussaineHoltz, Per-OlofKarlsson, Fredrik K

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