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Optical and Structural Characterization of GaN Based Hybrid Structures and Nanorods
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

GaN belongs to the group III nitrides and is today the material of choice for efficient blue light emission, enabling solid state white lighting by combining red, blue and green light emitting diodes (LED) or by having a blue LED illuminating a phosphor. By combining GaN quantum well (QW) structures with colloids, nanoparticles or polyfluorene films, LEDs may be fabricate at lower cost. Such hybrid structures are promising for future micro-light sources in full-color displays, sensors and imaging systems. In this work, hybrid structures based on an MOCVD grown GaN QW sandwiched between two layers of AlGaN have been studied. On top of the structure, colloidal ZnO nano-crystals were deposited by spin-coating. Time-resolved photoluminescence was used to investigate the QW exciton dynamics in these hybrids depending on the cap layer thickness. From comparison of the recombination rate in the bare QW structure and the hybrid, the efficiency of the non-radiative resonant energy transfer between the QW and the nano-crystals could be obtained.

Bulk GaN of large area is difficult to synthesize. Thus, due to lack of native substrates, GaN-based structures are grown on SiC or sapphire, which results in high threading dislocation density in the active layer of the device. Fabricating GaN nanorods (NR) can be a way to produce GaN with lower defect density since threading dislocations are annihilated toward the NR wall during growth. Here, GaN(0001) NRs grown on Si(111) substrates by magnetron sputter epitaxy using a liquid Ga target have been investigated. Sputter deposition has the advantage of being easy to scale up for depositions on large surfaces. It is also possible to deposit at lower temperatures, which allows the use of substrates with lower decomposition temperature. In the second paper of this thesis, optical and structural properties of sputtered GaN NRs have been studied.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. , 45 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1703
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-113741DOI: 10.3384/lic.diva-113741ISBN: 978-91-7519-141-6 (print)OAI: oai:DiVA.org:liu-113741DiVA: diva2:784420
Presentation
2015-02-27, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 14:30 (Swedish)
Opponent
Supervisors
Funder
Swedish Energy Agency
Available from: 2015-01-29 Created: 2015-01-29 Last updated: 2015-09-22Bibliographically approved
List of papers
1. Dynamic properties of excitons in ZnO/AlGaN/GaN hybrid nanostructures
Open this publication in new window or tab >>Dynamic properties of excitons in ZnO/AlGaN/GaN hybrid nanostructures
2015 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, no 7889, 1-5 p.Article in journal (Refereed) Published
Abstract [en]

Hybrid samples based on ZnO colloidal nanocrystals (NCs) deposited on AlGaN/GaN quantum well (QW) structures with different top barrier thickness d = 3, 6 and 9 nm are studied by time-resolved photoluminescence. Thermal behavior of the QW exciton lifetime in the hybrids and in the bare QW structures has been compared and it has been found that the QW exciton recombination rate increases in the hybrid having d = 3 nm and decreases in the hybrid with d = 6 nm, while no change has been observed for the structure with d = 9 nm. It is suggested that non-radiative resonance energy transfer from the QW excitons to the ZnO NCs and a variation of the surface potential can both influence the QW exciton lifetime in the hybrids.

Place, publisher, year, edition, pages
Nature Publishing Group, 2015
Keyword
Ultrafast photonics; Two-dimensional materials
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113739 (URN)10.1038/srep07889 (DOI)000348028300008 ()25601650 (PubMedID)
Note

Article

Available from: 2015-01-29 Created: 2015-01-29 Last updated: 2017-12-05Bibliographically approved
2. Stacking fault related luminescence in GaN nanorods
Open this publication in new window or tab >>Stacking fault related luminescence in GaN nanorods
Show others...
2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528Article in journal (Refereed) Published
Abstract [en]

Optical and structural properties are presented for GaN nanorods grown in the [0001]direction on Si(111) substrates by direct-current reactive magnetron sputter epitaxy.Transmission electron microscopy reveals clusters of dense stacking faults (SFs) regularlydistributed along the c-axis. A strong emission at ~3.42 eV associated with basal plane SFsdemonstrates thermal stability up to room temperatures together with a relatively shortrecombination time suggesting carrier localization in the system similar to multiple quantumwells.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015
Keyword
GaN nanorods, stacking faults, time-resolved photoluminescence, recombination time, multiple quantum wells, sputtering
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113740 (URN)10.1088/0957-4484/26/35/355203 (DOI)000360947200008 ()
Note

Funding: Swedish Research Council (VR); SFF; Angpanneforeningen

Available from: 2015-01-29 Created: 2015-01-29 Last updated: 2017-12-05Bibliographically approved

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