{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T12:56:26Z","timestamp":1760014586490,"version":"3.41.2"},"reference-count":74,"publisher":"AIP Publishing","issue":"18","license":[{"start":{"date-parts":[[2023,11,9]],"date-time":"2023-11-09T00:00:00Z","timestamp":1699488000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2023,11,9]],"date-time":"2023-11-09T00:00:00Z","timestamp":1699488000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2023,11,14]]},"abstract":"<jats:p>AlxGa1\u2212xN\/GaN high-electron-mobility transistor (HEMT) structures are key components in electronic devices operating at gigahertz or higher frequencies. In order to optimize such HEMT structures, understanding their electronic response at high frequencies and room temperature is required. Here, we present a study of the room temperature free charge carrier properties of the two-dimensional electron gas (2DEG) in HEMT structures with varying Al content in the AlxGa1\u2212xN barrier layers between x=0.07 and x=0.42. We discuss and compare 2DEG sheet density, mobility, effective mass, sheet resistance, and scattering times, which are determined by theoretical calculations, contactless Hall effect, capacitance-voltage, Eddy current, and cavity-enhanced terahertz optical Hall effect (THz-OHE) measurements using a low-field permanent magnet (0.6\u2009T). From our THz-OHE results, we observe that the measured mobility reduction from x=0.13 to x=0.42 is driven by the decrease in 2DEG scattering time, and not the change in effective mass. For x&amp;lt;0.42, the 2DEG effective mass is found to be larger than for electrons in bulk GaN, which in turn, contributes to a decrease in the principally achievable mobility. From our theoretical calculations, we find that values close to 0.3m0 can be explained by the combined effects of conduction band nonparabolicity, polarons, and hybridization of the electron wavefunction through penetration into the barrier layer.<\/jats:p>","DOI":"10.1063\/5.0163754","type":"journal-article","created":{"date-parts":[[2023,11,9]],"date-time":"2023-11-09T11:04:04Z","timestamp":1699527844000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":6,"title":["Room temperature two-dimensional electron gas scattering time, effective mass, and mobility parameters in Al<i>x<\/i>Ga1\u2212<i>x<\/i>N\/GaN heterostructures (0.07\u2009\u2264\u2009<i>x<\/i>\u2009\u2264\u20090.42)"],"prefix":"10.1063","volume":"134","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2758-6967","authenticated-orcid":false,"given":"Sean","family":"Knight","sequence":"first","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"},{"name":"Solid State Physics and NanoLund, Lund University 3 , 22100 Lund, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7344-1518","authenticated-orcid":false,"given":"Steffen","family":"Richter","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"},{"name":"Solid State Physics and NanoLund, Lund University 3 , 22100 Lund, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4902-5383","authenticated-orcid":false,"given":"Alexis","family":"Papamichail","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"}]},{"given":"Philipp","family":"K\u00fchne","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6363-4962","authenticated-orcid":false,"given":"Nerijus","family":"Armakavicius","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-7416-1732","authenticated-orcid":false,"given":"Shiqi","family":"Guo","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0399-8369","authenticated-orcid":false,"given":"Axel R.","family":"Persson","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 4 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7626-1181","authenticated-orcid":false,"given":"Vallery","family":"Stanishev","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, Sweden"},{"name":"Terahertz Materials Analysis Center (THeMAC), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8143-1088","authenticated-orcid":false,"given":"Viktor","family":"Rindert","sequence":"additional","affiliation":[{"name":"Solid State Physics and NanoLund, Lund University 3 , 22100 Lund, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9140-6724","authenticated-orcid":false,"given":"Per O. \u00c5.","family":"Persson","sequence":"additional","affiliation":[{"name":"Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 4 , 581 83 Link\u00f6ping, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2602-1523","authenticated-orcid":false,"given":"Plamen P.","family":"Paskov","sequence":"additional","affiliation":[{"name":"Center for III-Nitride Technology (C3NiT\u2014Janz\u00e9n), Department of Physics, Chemistry and Biology (IFM), Link\u00f6ping University 1 , 581 83 Link\u00f6ping, 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Link\u00f6ping University 2 , 581 83 Link\u00f6ping, Sweden"},{"name":"Solid State Physics and NanoLund, Lund University 3 , 22100 Lund, Sweden"}]}],"member":"317","published-online":{"date-parts":[[2023,11,9]]},"reference":[{"key":"2023110911030711000_c1","doi-asserted-by":"publisher","first-page":"1173","DOI":"10.1109\/LED.2020.3005337","article-title":"360\u2009GHz fMAX graded-channel AlGaN\/GaN HEMTs for mmW low-noise applications","volume":"41","year":"2020","journal-title":"IEEE Electron Device Lett."},{"key":"2023110911030711000_c2","doi-asserted-by":"publisher","first-page":"3222","DOI":"10.1063\/1.369664","article-title":"Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN\/GaN heterostructures","volume":"85","year":"1999","journal-title":"J. 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