Far-infrared transmission in GaN, AlN, and AlGaN thin films grown by molecular beam epitaxy
- Institut Jaume Almera, Consell Superior d'Investigacions Cientifiques (CSIC), Lluis Sole i Sabaris s.n, 08028 Barcelona, Catalonia (Spain)
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
- ISOM-Departamento Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica, 28040 Madrid (Spain)
We present a far-infrared transmission study on group-III nitride thin films. Cubic GaN and AlN layers and c-oriented wurtzite GaN, AlN, and Al{sub x}Ga{sub 1-x}N (x<0.3) layers were grown by molecular beam epitaxy on GaAs and Si(111) substrates, respectively. The Berreman effect allows us to observe simultaneously the transverse optic and the longitudinal optic phonons of both the cubic and the hexagonal films as transmission minima in the infrared spectra acquired with obliquely incident radiation. We discuss our results in terms of the relevant electromagnetic theory of infrared transmission in cubic and wurtzite thin films. We compare the infrared results with visible Raman-scattering measurements. In the case of films with low scattering volumes and/or low Raman efficiencies and also when the Raman signal of the substrate material obscures the weaker peaks from the nitride films, we find that the Berreman technique is particularly useful to complement Raman spectroscopy.
- OSTI ID:
- 21137425
- Journal Information:
- Journal of Applied Physics, Vol. 104, Issue 3; Other Information: DOI: 10.1063/1.2968242; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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