Optical characteristics of nanocrystalline AlxGa1-xN thin films deposited by hollow cathode plasma-assisted atomic layer deposition
Kemal Okyay, A.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
AVS Science and Technology Society
Item Usage Stats
MetadataShow full item record
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.
Atomic layer deposition
Near infrared spectroscopy
Optical band gaps
Pulsed laser deposition
X ray diffraction
X ray diffraction analysis
Aluminum nitride (AlN)
Extinction coefficient (k)
Gallium nitrides (GaN)
Low deposition temperature
Post deposition annealing
Spectroscopic ellipsometry measurements
Published Version (Please cite this version)http://dx.doi.org/10.1116/1.4870381
Showing items related by title, author, creator and subject.
Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition Ozgit, C.; Donmez I.; Alevli, M.; Biyikli, N. (2012)We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ...
Effect of film thickness on the electrical properties of AlN films prepared by plasma-enhanced atomic layer deposition Altuntas, H.; Ozgit Akgun, C.; Donmez, I.; Biyikli, N. (Institute of Electrical and Electronics Engineers Inc., 2015)In this paper, AlN thin films with two different thicknesses, i.e., 7 and 47 nm, were deposited at 200 °C on p-type Si substrates by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia. To investigate ...
Metal-semiconductor-metal ultraviolet photodetectors based on gallium nitride grown by atomic layer deposition at low temperatures Tekcan, B.; Ozgit Akgun, C.; Bolat, S.; Biyikli, N.; Okyay, A., K. (SPIE, 2014)Proof-of-concept, first metal-semiconductor-metal ultraviolet photodetectors based on nanocrystalline gallium nitride (GaN) layers grown by low-temperature hollow-cathode plasma-assisted atomic layer deposition are ...