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dc.contributor.authorGoldenberg, E.en_US
dc.contributor.authorOzgit-Akgun, C.en_US
dc.contributor.authorBiyikli, N.en_US
dc.contributor.authorKemal Okyay, A.en_US
dc.date.accessioned2016-02-08T11:00:57Z
dc.date.available2016-02-08T11:00:57Z
dc.date.issued2014en_US
dc.identifier.issn0734-2101
dc.identifier.urihttp://hdl.handle.net/11693/26520
dc.description.abstractGallium nitride (GaN), aluminum nitride (AlN), and AlxGa 1-xN films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200 °C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al xGa1-xN films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2 nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4 nm when the annealing duration increased from 30 min to 2 h (800 °C). For all films, the average optical transmission was ∼ 85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and AlxGa1-xN were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (λ = 550 nm) with the increased Al content x (0 ≤ x ≤ 1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400 nm). Postdeposition annealing at 900 °C for 2 h considerably lowered the refractive index value of GaN films (2.33-1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95 eV, and it decreased to 3.90 eV for films annealed at 800 °C for 30 min and 2 h. On the other hand, this value increased to 4.1 eV for GaN films annealed at 900 °C for 2 h. This might be caused by Ga 2O3 formation and following phase change. The optical bandgap value of as-deposited AlxGa1-xN films decreased from 5.75 to 5.25 eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not affect the bandgap of Al-rich films. © 2014 American Vacuum Society.en_US
dc.language.isoEnglishen_US
dc.source.titleJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Filmsen_US
dc.relation.isversionofhttp://dx.doi.org/10.1116/1.4870381en_US
dc.subjectAnnealingen_US
dc.subjectAtomic layer depositionen_US
dc.subjectCathodesen_US
dc.subjectDepositionen_US
dc.subjectGallium alloysen_US
dc.subjectGallium nitrideen_US
dc.subjectMetallic filmsen_US
dc.subjectNear infrared spectroscopyen_US
dc.subjectOptical band gapsen_US
dc.subjectPulsed laser depositionen_US
dc.subjectRefractive indexen_US
dc.subjectSpectroscopic ellipsometryen_US
dc.subjectThin filmsen_US
dc.subjectX ray diffractionen_US
dc.subjectX ray diffraction analysisen_US
dc.subjectZinc sulfideen_US
dc.subjectAluminum nitride (AlN)en_US
dc.subjectExtinction coefficient (k)en_US
dc.subjectGallium nitrides (GaN)en_US
dc.subjectLow deposition temperatureen_US
dc.subjectOptical characteristicsen_US
dc.subjectPolycrystalline wurtziteen_US
dc.subjectPost deposition annealingen_US
dc.subjectSpectroscopic ellipsometry measurementsen_US
dc.subjectAluminumen_US
dc.titleOptical characteristics of nanocrystalline AlxGa1-xN thin films deposited by hollow cathode plasma-assisted atomic layer depositionen_US
dc.typeArticleen_US
dc.departmentDepartment of Electrical and Electronics Engineering
dc.citation.volumeNumber32en_US
dc.citation.issueNumber3en_US
dc.identifier.doi10.1116/1.4870381en_US
dc.publisherAVS Science and Technology Societyen_US


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