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Carrier localization in m-plane InGaN/GaN quantum wells probed by scanning near field optical spectroscopy
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.ORCID iD: 0000-0002-4606-4865
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2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 15, 151106- p.Article in journal (Refereed) Published
Abstract [en]

Scanning near field optical microscopy (SNOM) was applied to study the carrier localization in single InGaN/GaN quantum well structures grown on nonpolar m-plane GaN substrates. Dual localization potential consisting of hundreds of nanometers- to micrometer-size areas as well as smaller localization centers were identified from the SNOM scans and near field photoluminescence spectral widths. The localization areas were found to align along the [0001] direction, which was attributed to partial strain relaxation at the monolayer steps. (C) 2010 American Institute of Physics. [doi:10.1063/1.3502482]

Place, publisher, year, edition, pages
2010. Vol. 97, no 15, 151106- p.
Keyword [en]
EMISSION, PHONON, GAN
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26283DOI: 10.1063/1.3502482ISI: 000283216900006Scopus ID: 2-s2.0-77958092390OAI: oai:DiVA.org:kth-26283DiVA: diva2:385781
Funder
Swedish Research Council
Note
QC 20110112Available from: 2011-01-12 Created: 2010-11-21 Last updated: 2012-11-01Bibliographically approved
In thesis
1. Localization effects in ternary nitride semiconductors
Open this publication in new window or tab >>Localization effects in ternary nitride semiconductors
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

InGaN based blue and near-ultraviolet light emitting diodes and laser diodes have been successfully commercialized for many applications such as general lighting, display backlighting and high density optical storage devices. Despite having a comparably high defect density, these devices are known for their efficient operation, which is attributed to localization in potential fluctuations preventing carriers from reaching the centers of nonradiative recombination. Nitride research is currently headed towards improving deep ultraviolet AlGaN and green InGaN emitters with higher Al and In molar fractions. The efficiency of these devices trails behind the blue counterparts as the carrier localization does not seem to aid in supressing nonradiative losses. In addition, the operation of ternary nitride heterostructure based devices is further complicated by the presence of large built-in electric fields. Although the problem can be ameliorated by growing structures in nonpolar or semipolar directions, the step from research to production still awaits.

In this thesis, carrier dynamics and localization effects have been studied in three different nitride ternary compounds: AlGaN epitaxial layers and quantum wells with high Al content, nonpolar m-plane InGaN/GaN quantum wells and lattice matched AlInN/GaN heterostructures. The experimental methods of this work mainly consist of spectroscopy techniques such as time-resolved photoluminescence and differential transmission pump-probe measurements as well as spatial photoluminescence mapping by means of scanning near-field microscopy.

The comparison of luminescence and differential transmission measurements has allowed estimating the localization depth in AlGaN quantum wells. Additionally, it has been demonstrated that the polarization degree of luminescence from m-InGaN quantum wells decreases as carriers diffuse to localization centers.What is more, dual-scale localization potential has been evidenced by near-field measurements in both AlGaN and m-InGaN. Larger scale potential fluctuation have been observed directly and the depth of nanoscopic localization has been estimated theoretically from the recorded linewidth of the near-field spectra. Lastly, efficient carrier transport has been observed through AlInN layer despite large alloy inhomogeneities evidenced by broad luminescence spectra and the huge Stokes shift. Inhomogeneous luminescence from the underlying GaN layer has been linked to the fluctuations of the built-in electric field at the AlInN/GaN interface.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xii, 70 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:18
Keyword
AlGaN, InGaN, AlInN, LEDs, near-field microscopy, carrier dynamics, alloy fluctuations, carrier localization, built-in electric field, nonpolar planes, polarized luminescence
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-104290 (URN)978-91-7501-530-9 (ISBN)
Public defence
2012-11-19, sal C2, KTH-Electrum, Isafjordsgatan 26, Kista, 10:30 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20121101

Available from: 2012-11-01 Created: 2012-10-31 Last updated: 2012-11-01Bibliographically approved

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Marcinkevicius, Saulius

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