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Bandgap Engineering and Optical Constants of YxAl1-xN Alloys
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2837-3656
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2013 (English)In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 52, no 8Article in journal (Refereed) Published
Abstract [en]

We study wurtzite Yx Al1-xN (0 andlt;= x andlt;= 0:22) films with (0001) orientation deposited by magnetron sputtering epitaxy on Si(100) substrates and we determine the alloys band gap energies and optical constants. Room temperature spectroscopic ellipsometry (SE) is employed in the energy range from 1 to 6.3 eV, and data modeling based on the standard dielectric function model is used. As a result of the SE data analysis the Yx Al1-xN refractive index and extinction coefficient are determined. The band gap of Yx Al1-xN is found to decrease linearly from 6.2 eV (x=0) down to 4.5 eV (x=0:22). We further observe an increase of the refractive index with increasing Y content; from 1.93 to 2.20 (at 2 eV) for x=0 and 0.22, respectively, reflecting the increase in material density.

Place, publisher, year, edition, pages
Japan Society of Applied Physics , 2013. Vol. 52, no 8
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-98153DOI: 10.7567/JJAP.52.08JM02ISI: 000323883100159OAI: oai:DiVA.org:liu-98153DiVA: diva2:652282
Note

Funding Agencies|FCT|REF:SFRH/BPD/66818/2009|Swedish Research Council (VR)|2010-3848|Linko "ping Linnaeus Initiative on Nanoscale Functional Materials (LiLiNFM)||Swedish Governmental Agency for Innovation Systems (VINNOVA)|2011-03486|

Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06
In thesis
1. Metastable ScAlN and YAlN Thin Films Grown by Reactive Magnetron Sputter Epitaxy
Open this publication in new window or tab >>Metastable ScAlN and YAlN Thin Films Grown by Reactive Magnetron Sputter Epitaxy
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Metastable ScxAl1-xN and YxAl1-xN thin films were deposited in an ultra high vacuum system using reactive magnetron sputter epitaxy from elemental Al, Sc, and Y targets in Ar/N2 gas mixture. Their structural, electrical, optical, mechanical, and piezoelectrical properties were investigated by using the transmission electron microscopy, x-ray diffraction, spectroscopic ellipsometry, I-V and C-V measurements, nanoindentation, and two different techniques for piezoelectric characterization: piezoresponse force microscopy and double beam interferometry.

Compared to AlN, improved electromechanical coupling and increase in piezoelectric response was found in ScxAl1-xN/TiN/Al2O3 structures with Sc content up to x=0.2. Decreasing the growth temperature down to 400 °C improved the microstructure and crystalline quality of the material. Microstructure of the films had a stronger influence on piezoelectric properties than the crystalline quality, which affected the leakage currents. When x was increased from x=0 to x=0.3, the hardness and reduced Young’s modulus Er showed a decrease from 17 GPa to 11 GPa, and 265 GPa down to 224 GPa, respectively. In ScxAl1-xN/InyAl1-yN superlattices, ScxAl1-xN layers negative lattice mismatched to In-rich InyAl1-yN were found to be stable at higher Sc concentration (x=0.4) than lattice-matched or positive lattice mismatched layers, confirmed by first principle (ab initio) calculations using density-functional formalism.

Al-rich YxAl1-xN thin films were synthesized and reported for the first time. Formation of solid solution was observed up to x=0.22 and an increase in growth temperature up to 900°C improved the crystalline quality of the YxAl1-xN films. The band gap of YxAl1-xN decreased from 6.2 eV for AlN down to 4.5 eV (x=0.22) and was shown to follow Vegard’s rule. Refractive indices and extinction coefficients were also determined. Lattice constants of wurtzite YxAl1-xN measured experimentally are in good agreement with theoretical predictions obtained through ab initio calculations. The mixing enthalpy

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1564
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-103832 (URN)10.3384/diss.diva-103832 (DOI)978-91-7519-434-9 (ISBN)
Public defence
2014-02-21, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2014-01-29 Created: 2014-01-29 Last updated: 2016-08-31Bibliographically approved

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Zukauskaite, AgneBirch, JensHultman, LarsDarakchieva, Vanya

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