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For high-Al-content AlxGa1\u2212xN, a two mode behavior is observed for both transverse and longitudinal branches of the infrared-active modes with E1 symmetry, while a single mode behavior is found for the longitudinal modes with A1(LO) symmetry. We report their mode dependencies on the Al content. We determine and discuss static and high frequency dielectric constants depending on x. From the analysis of the optical Hall effect data, we determine the effective mass parameter in high-Al-content AlxGa1\u2212xN alloys and its composition dependence. Within the experimental uncertainty limits, the effective mass parameters are found isotropic, which depend linearly on the Al content. The combination of all data permits the quantification of the free electron density N and mobility parameters \u03bc.<\/jats:p>","DOI":"10.1063\/1.4983765","type":"journal-article","created":{"date-parts":[[2017,5,24]],"date-time":"2017-05-24T13:47:56Z","timestamp":1495633676000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":19,"title":["Infrared dielectric functions, phonon modes, and free-charge carrier properties of high-Al-content Al<i>x<\/i>Ga1\u2212<i>x<\/i>N alloys determined by mid infrared spectroscopic ellipsometry and optical Hall effect"],"prefix":"10.1063","volume":"121","author":[{"given":"S.","family":"Sch\u00f6che","sequence":"first","affiliation":[{"name":"University of Nebraska-Lincoln 1 Department of Electrical and Computer Engineering, and Center for Nanohybrid Functional Materials, , Lincoln, NE 68588-0511, USA"}]},{"given":"T.","family":"Hofmann","sequence":"additional","affiliation":[{"name":"University of Nebraska-Lincoln 1 Department of Electrical and Computer Engineering, and Center for Nanohybrid Functional Materials, , Lincoln, NE 68588-0511, USA"},{"name":"Link\u00f6ping University 2 Terahertz Materials Analysis Center, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]},{"given":"D.","family":"Nilsson","sequence":"additional","affiliation":[{"name":"Link\u00f6ping University 3 Semiconductor Materials Division, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]},{"given":"A.","family":"Kakanakova-Georgieva","sequence":"additional","affiliation":[{"name":"Link\u00f6ping University 3 Semiconductor Materials Division, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]},{"given":"E.","family":"Janz\u00e9n","sequence":"additional","affiliation":[{"name":"Link\u00f6ping University 3 Semiconductor Materials Division, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8827-7404","authenticated-orcid":false,"given":"P.","family":"K\u00fchne","sequence":"additional","affiliation":[{"name":"Link\u00f6ping University 2 Terahertz Materials Analysis Center, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]},{"given":"K.","family":"Lorenz","sequence":"additional","affiliation":[{"name":"IPFN, Instituto Superior T\u00e9cnico, Universidade de Lisboa 4 , Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6238-663X","authenticated-orcid":false,"given":"M.","family":"Schubert","sequence":"additional","affiliation":[{"name":"University of Nebraska-Lincoln 1 Department of Electrical and Computer Engineering, and Center for Nanohybrid Functional Materials, , Lincoln, NE 68588-0511, USA"},{"name":"Link\u00f6ping University 2 Terahertz Materials Analysis Center, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"},{"name":"Leibniz Institute for Polymer Research 5 , Dresden, Germany"}]},{"given":"V.","family":"Darakchieva","sequence":"additional","affiliation":[{"name":"Link\u00f6ping University 2 Terahertz Materials Analysis Center, Department of Physics, Chemistry and Biology (IFM), , Link\u00f6ping SE-58183, Sweden"}]}],"member":"317","published-online":{"date-parts":[[2017,5,24]]},"reference":[{"key":"2023062517564488300_c1","doi-asserted-by":"publisher","first-page":"122105","DOI":"10.1063\/1.4821183","volume":"103","year":"2013","journal-title":"Appl. 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