Optical constants of epitaxial AlGaN films and their temperature dependence
作者:
D. Brunner,
H. Angerer,
E. Bustarret,
F. Freudenberg,
R. Ho¨pler,
R. Dimitrov,
O. Ambacher,
M. Stutzmann,
期刊:
Journal of Applied Physics
(AIP Available online 1997)
卷期:
Volume 82,
issue 10
页码: 5090-5096
ISSN:0021-8979
年代: 1997
DOI:10.1063/1.366309
出版商: AIP
数据来源: AIP
摘要:
We have studied the dependence of the absorption edge and the refractive index of wurtziteAlxGa1−xNfilms on temperature and composition using transmission and photothermal deflection spectroscopy. The Al molar fraction of theAlxGa1−xNfilms grown by plasma induced molecular beam epitaxy was varied through the entire range of composition(0⩽x⩽1).We determined the absorption edges ofAlxGa1−xNfilms and a bowing parameter of1.3±0.2 eV.The refractive index in the photon energy range between 1 and 5.5 eV and temperatures between 7 and 295 K was deduced from the interference fringes. The static refractive indexn(0)changed from 2.29 for GaN to 1.96 for AlN at room temperature. A variation of temperature from 295 to 7 K resulted in a decrease of refractive index (at photon energies close to the band gap) by0.05±0.01and in an energy shift of the absorption edge of about64±5 meVindependent of the Al content of the films. Using the Kramers–Kronig dispersion relation and an approximation for the dispersion coefficient for photon energies near the band gap, the refractive index could be described as a function of photon energy, Al content, and temperature. ©1997 American Institute of Physics.
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