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InGaN Quantum Dots Grown on GaN Pyramid Arrays
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Selective-area growth (SAG) of InGaN on GaN pyramids, which allows the formation of additional hybrid quantum structures, including quantum wires and quantum dots (QDs) in a site-controlled fashion, is attractive for both fundamental research and device application. The site-controlled growth of QDs showing sharp emission lines is seen as the first step toward the frontier quantum information application (QIA). Note that, in such case, one QD represents one device unless the challenge of fabricating identical QDs is overcome.

The concept of SAG GaN pyramids hosting InGaN QDs has been reported since 2000. However, the observation of sharp emission lines, which can be ascribed to three-dimensional carrier confinement in QDs, seems to be occasional.

The main outcome of this work is the investigation of the InGaN QDs grown on GaN hexagonal pyramids. This work covers the formation mechanism of InGaN QDs to the emission properties of individual InGaN QDs. A modified SAG approach to obtain InGaN QDs emitting photons with heralded polarization directions is also demonstrated. The inherent high polarization degree of photons emitted by InGaN QDs together with heralded polarization direction reveals a promising potential for the direct generation of linearly-polarized photons by site-controlled InGaN QDs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 59 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1534
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-97412ISBN: 978-91-7519-550-6 (print)OAI: oai:DiVA.org:liu-97412DiVA: diva2:647675
Public defence
2013-09-05, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2013-09-16Bibliographically approved
List of papers
1. Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays
Open this publication in new window or tab >>Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays
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2011 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 6, 2415-2418 p.Article in journal (Refereed) Published
Abstract [en]

Fabrication of single InGaN quantum dots (QDs) on top of GaN micropyramids is reported. The formation of single QDs is evidenced by showing single sub-millielectronvolt emission lines in microphotoluminescence (mu PL) spectra. Tunable QD emission energy by varying the growth temperature of the InGaN layers is also demonstrated. From mu PL, it is evident that the QDs are located in the apexes of the pyramids. The fact that the emission lines of the QDs are linear polarized in a preferred direction implies that the apexes induce unidirected anisotropic fields to the QDs. The single emission lines remain unchanged with increasing the excitation power and/or crystal temperature. An in-plane elongated QD forming a shallow potential with an equal number of trapped electrons and holes is proposed to explain the absence of other exciton complexes.

Place, publisher, year, edition, pages
American Chemical Society, 2011
Keyword
InGaN, quantum dots, pyramid, exciton, photoluminescence
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-69169 (URN)10.1021/nl200810v (DOI)000291322600038 ()
Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-12-11Bibliographically approved
2. Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD
Open this publication in new window or tab >>Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD
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2013 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 363, 287-293 p.Article in journal (Refereed) Published
Abstract [en]

Hexagonal GaN pyramids have been fabricated by hot-wall metal organic chemical vapor deposition (hot-wall MOCVD) and the growth evolution have been studied. It was concluded that the pyramid growth can be divided into two regimes separated by the adsorption kinetics of the {1101} surfaces of the pyramids. In the adsorption regime, the pyramids grow simultaneously in the <1101> and [0001] -directions. In the zero-adsorption regime the pyramids grow only in the [0001] direction. Thus the pyramid growth ceases when the (0001) facet growth has been terminated. Large arrays consisting of highly uniform pyramids with apex radii of 3 nm or less were achieved in the zeroadsorption regime. The growth-regime type was concluded to have a large impact on the uniformity degradation of the pyramids, and their optical properties. The impacts of threading dislocations which enter the pyramid from underneath are also discussed.

Keyword
A3. Hot wall epitaxy A3. Metalorganic vapor phase epitaxy A3. Selective epitaxy B1. Nitrides
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-79317 (URN)10.1016/j.jcrysgro.2012.11.014 (DOI)000313205400047 ()
Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2017-12-07Bibliographically approved
3. InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids
Open this publication in new window or tab >>InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 30, 305708- p.Article in journal (Refereed) Published
Abstract [en]

Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal–organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2012
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-79321 (URN)10.1088/0957-4484/23/30/305708 (DOI)000306333500030 ()
Available from: 2012-07-10 Created: 2012-07-10 Last updated: 2017-12-07Bibliographically approved
4. Controlled Growth of GaN Pyramidal template hosting InGaN Quantum Dots
Open this publication in new window or tab >>Controlled Growth of GaN Pyramidal template hosting InGaN Quantum Dots
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The emission properties of InGaN grown on hexagonal GaN pyramids with various pitch distances (PD) are studied. Emissions associated with InGaN quantum wells (QWs) and InGaN quantum dots (QDs) can be identified. The emission energies of InGaN QWs and QDs shift toward opposite directions with increasing PD; red-shift for QWs and blue-shift for QDs. Based on the source supply mechanism in a selective area growth process, the formation of InGaN QDs on GaN pyramids is believed to be a combined effect of Stranski-Krastanow growth mode and spinodal decomposition taking place at the microscopic (0001) surfaces on GaN pyramids.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97411 (URN)
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2016-08-31Bibliographically approved
5. The charged exciton in an InGaN quantum dot on a GaN pyramid
Open this publication in new window or tab >>The charged exciton in an InGaN quantum dot on a GaN pyramid
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2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 1Article in journal (Refereed) Published
Abstract [en]

The emission of a charged exciton in an InGaN quantum dot (QD) on top of a GaN pyramid is identified experimentally. The intensity of the charged exciton exhibits the expected competition with that of the single exciton, as observed in temperature-dependent micro-photoluminescence measurements, performed with different excitation energies. The non-zero charge state of this complex is further supported by time resolved micro-photoluminescence measurements, which excludes neutral alternatives of biexciton. The potential fluctuations in the vicinity of the QD that localizes the charge carriers are proposed to be responsible for the unequal supply of electrons and holes into the QD.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-95961 (URN)10.1063/1.4812984 (DOI)000321497200036 ()
Note

Funding Agencies|NANO-N consortium||Swedish Foundation for Strategic Research (SSF)||

Available from: 2013-08-19 Created: 2013-08-12 Last updated: 2017-12-06
6. The Dynamics of Charged and Neutral Excitons in an InGaN Quantum Dot on a GaN Pyramid
Open this publication in new window or tab >>The Dynamics of Charged and Neutral Excitons in an InGaN Quantum Dot on a GaN Pyramid
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The neutral (X0) and negatively charged excitons (X-) in an InGaN QD on a GaN pyramid is studied by the timeintegrated micro-photoluminescence (μPL) and time-resolved micro-photoluminescence (TRμPL) microcopies. Both X0 and X- exhibit mono-exponential decay curves with fitted lifetimes of 310 and 140 ps, respectively. Neither energy shifts nor changes in the life times X0 and X- with increasing excitation power were observed, indicating the QD is small and free from the quantum confine Stark effect. The TRμPL is not only a powerful technique for studying the dynamics of exciton in QDXs, but also for the identification of exciton complexes in QDs.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97416 (URN)
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2015-01-23Bibliographically approved
7. Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots
Open this publication in new window or tab >>Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots
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2014 (English)In: Light: Science & Applications, ISSN 2095-5545, Vol. 3, e139Article in journal (Refereed) Published
Abstract [en]

Semiconductor quantum dots (QDs) have been demonstrated viable for the emission of single photons on demand during the past decade. However, the synthesis of QDs emitting photons with pre-defined and deterministic polarization vectors has proven arduous. The access of linearly-polarized photons is essential for various applications. In this report, a novel concept to directly generate linearly-polarized photons is presented. This concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which predefined orientations herald the polarization vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultracompact arrays of photon emitters, with a controlled polarization direction for each individual QD emitter.

Place, publisher, year, edition, pages
Nature Publishing Group, 2014
Keyword
GaN; InGaN; photoluminescence; polarized emission; quantum dot
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97417 (URN)10.1038/lsa.2014.20 (DOI)000331998400011 ()
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2017-04-11Bibliographically approved

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