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Spin-dependent recombination in Ga(In)NAs alloys
Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The abilities to control and manipulate electron spin, especially in semiconductors, lead to many interesting proposals for spin-functional devices in future spintronics and quantum information technology. A key requirement for the success of these proposals is that the spin functionality should be operational at room temperature (RT), which remains as a great challenge. Very recently, spin-dependent recombination (SDR) via paramagnetic defects that dominate in carrier recombination, i.e Gai - interstitial defects in Ga(In)NAs alloys, has been shown to turn the material into a highly efficient defectengineered spin filter operating at RT and without requiring an external applied field. This finding has demonstrated the great potential of such a spin filter as an efficient spin source, which is capable of generating up to 90% electron spin polarization at RT.

Essential to realization of this attractive application in spintronics is a fundamental understanding of this alloy system and their related spin filtering defects. Therefore, factors controlling this spin filter must be studied, understood and optimized. In this licentiate thesis, we aim at optimization of the spin filtering effect in Ga(In)NAs alloys and the related quantum structures by studying influence of material fabrication techniques, post growth treatments and material structures. In paper I, we employed the optically detected magnetic resonance (ODMR) technique to study formation of Ga interstitial-related defects in Ga(In)NAs alloys. We showed that these spin-filtering defects are common grown-in defects in these alloys, independent of the employed fabrication techniques and post-growth annealing treatment. The defect formation was suggested to be thermodynamically favorable in the presence of nitrogen, possibly because of local strain compensation. In paper II, we further investigated the role of post-growth hydrogen treatment in the spin filtering effect in GaNAs epilayers and GaNAs/GaAs multiple quantum wells (QWs). From optical orientation studies, we found that the hydrogen treatment has led to nearly complete quenching of the spin filtering effect. Together with a detailed ODMR study and a rate equation analysis, the observed effect of hydrogen was attributed to hydrogen passivation of the spin filtering defects, likely by formation of complexes between the Gai-interstitial defects and hydrogen. This finding also ruled out the possibility of hydrogen as a part of the spin filtering defects in the as-grown materials, though hydrogen is known to be commonly present during the growth process.

In Paper III, we examined the effectiveness of the spin filtering effect in the GaNAs/GaAs QWs as a function of QW width. Even with rather narrow QW widths of 3-9 nm, the spin filtering effect was shown to be efficient. It was further revealed that the spin filtering effect is more efficient in the wider QWs. From studies of transient behavior of photoluminescence and ODMR, it was concluded that this was mainly due to an increase in the sheet concentration of the spin filtering defects.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. , 34 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1533
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-77153Local ID: LIU-TEK-LIC-2012:18ISBN: 978-91-7519-875-0 (print)OAI: oai:DiVA.org:liu-77153DiVA: diva2:525198
Presentation
2012-05-30, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2017-03-27Bibliographically approved
List of papers
1. Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
Open this publication in new window or tab >>Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
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2009 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, 241904- p.Article in journal (Refereed) Published
Abstract [en]

Opticallydetected magnetic resonance measurements are carried out to study formationof Ga interstitial-related defects in Ga(In)NAs alloys. The defects, whichare among dominant nonradiative recombination centers that control carrier lifetimein Ga(In)NAs, are unambiguously proven to be common grown-in defectsin these alloys independent of the employed growth methods. Thedefects formation is suggested to become thermodynamically favorable because ofthe presence of nitrogen, possibly due to local strain compensation.

Place, publisher, year, edition, pages
American Institute of Physics, 2009
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-52858 (URN)10.1063/1.3275703 (DOI)
Note
Original Publication: Xingjun Wang, Yuttapoom Puttisong, C. W. Tu, Aaron J. Ptak, V. K. Kalevich, A. Yu. Egorov, L. Geelhaar, H. Riechert, Weimin Chen and Irina Buyanova, Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials, 2009, Applied Physics Letters, (95), 241904. http://dx.doi.org/10.1063/1.3275703 Copyright: American Institute of Physics http://www.aip.org/Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-03-27Bibliographically approved
2. Room temperature spin filtering effect in GaNAs: Role of hydrogen
Open this publication in new window or tab >>Room temperature spin filtering effect in GaNAs: Role of hydrogen
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2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, 152109- p.Article in journal (Refereed) Published
Abstract [en]

Effects of hydrogen on the recently discovered defect-engineered spin filtering in GaNAs are investigated by optical spin orientation and optically detected magnetic resonance. Post-growth hydrogen treatments are shown to lead to nearly complete quenching of the room-temperature spin-filtering effect in both GaNAs epilayers and GaNAs/GaAs multiple quantum wells, accompanied by a reduction in concentrations of Ga(i) interstitial defects. Our finding provides strong evidence for efficient hydrogen passivation of these spin-filtering defects, likely via formation of complexes between Gai defects and hydrogen, as being responsible for the Observed strong suppression of the spin-filtering effect after the hydrogen treatments.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2011
Keyword
gallium arsenide, gallium compounds, hydrogen, III-V semiconductors, interstitials, magnetic resonance, passivation, quenching (thermal), semiconductor epitaxial layers, semiconductor quantum wells, wide band gap semiconductors
National Category
Engineering and Technology Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-72139 (URN)10.1063/1.3651761 (DOI)000295883800045 ()
Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
3. Electron spin filtering by thin GaNAs/GaAs multiquantum wells
Open this publication in new window or tab >>Electron spin filtering by thin GaNAs/GaAs multiquantum wells
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2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, 052104- p.Article in journal (Refereed) Published
Abstract [en]

Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3-9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Ga-i interstitial defects).

Keyword
electron spin polarisation, gallium arsenide, III-V semiconductors, nitrogen compounds, photoluminescence, semiconductor quantum wells
National Category
Engineering and Technology Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-54084 (URN)10.1063/1.3299015 (DOI)000274319500045 ()
Available from: 2010-02-22 Created: 2010-02-22 Last updated: 2017-03-27Bibliographically approved

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