Academic Journal
Optical characteristics of nanocrystalline AlxGa1-xN thin films deposited by hollow cathode plasma-assisted atomic layer deposition
| العنوان: | Optical characteristics of nanocrystalline AlxGa1-xN thin films deposited by hollow cathode plasma-assisted atomic layer deposition |
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| المؤلفون: | Goldenberg, E., Ozgit-Akgun, C., Biyikli, N., Kemal Okyay, A. |
| المصدر: | Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films |
| بيانات النشر: | AVS Science and Technology Society |
| سنة النشر: | 2014 |
| المجموعة: | Bilkent University: Institutional Repository |
| مصطلحات موضوعية: | Annealing, Atomic layer deposition, Cathodes, Deposition, Gallium alloys, Gallium nitride, Metallic films, Near infrared spectroscopy, Optical band gaps, Pulsed laser deposition, Refractive index, Spectroscopic ellipsometry, Thin films, X ray diffraction, X ray diffraction analysis, Zinc sulfide, Aluminum nitride (AlN), Extinction coefficient (k), Gallium nitrides (GaN), Low deposition temperature, Optical characteristics, Polycrystalline wurtzite, Post deposition annealing, Spectroscopic ellipsometry measurements, Aluminum |
| الوصف: | Gallium 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. |
| نوع الوثيقة: | article in journal/newspaper |
| وصف الملف: | application/pdf |
| اللغة: | English |
| Relation: | http://dx.doi.org/10.1116/1.4870381; 7342101; http://hdl.handle.net/11693/26520 |
| DOI: | 10.1116/1.4870381 |
| الاتاحة: | http://hdl.handle.net/11693/26520 https://doi.org/10.1116/1.4870381 |
| رقم الانضمام: | edsbas.983059F4 |
| قاعدة البيانات: | BASE |
| DOI: | 10.1116/1.4870381 |
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