標題: Infrared reflectance of optical phonon modes in AlGaN epitaxial layers grown on sapphire substrates - art. no. 68941U
作者: Chen, Jun-Rong
Lu, Tien-Chang
Huang, Gen-Sheng
Ko, Tsung-Shine
Kuo, Hao-Chung
Wang, Shing-Chung
光電工程學系
Department of Photonics
關鍵字: AlGaN;sapphire;infrared reflectance;FTIR
公開日期: 2008
摘要: We reported the systematical study of optical properties of hexagonal AlxGa1-xN epitaxial films grown on c-sapphire substrate using metal-organic chemical vapor deposition. By performing Fourier transform infrared spectroscopy measurements, the high-frequency dielectric constants and phonon frequencies can be obtained by theoretically fitting the experimental infrared reflectance spectra using a four-phase layered model. The high-frequency dielectric constant of AlxGa1-xN varies between 4.98 and 4.52 for epsilon(infinity,perpendicular to) (polarization perpendicular to the optical axis) and between 4.95 and 4.50 for epsilon(infinity,//) (polarization parallel to the optical axis) respectively when the aluminum composition changes from 0.15 to 0.24. Furthermore, from experimental infrared reflectance spectra of AlxGa1-xN films, a specific absorption dip at 785 cm-1 was observed when the aluminum composition is larger than 0.24. The dip intensity increases and the dip frequency shifts from 785 to 812 cm(-1) as aluminum composition increases from 0.24 to 0.58. According to the reciprocal space map of x-ray diffraction measurements, the emergence of this dip could be resulted from the effects of strain relaxation in AlGaN epitaxial layers due to the large lattice mismatch between GaN and AlGaN epitaxial film.
URI: http://hdl.handle.net/11536/32453
http://dx.doi.org/10.1117/12.760296
ISBN: 978-0-8194-7069-0
ISSN: 0277-786X
DOI: 10.1117/12.760296
期刊: GALLIUM NITRIDE MATERIALS AND DEVICES III
Volume: 6894
起始頁: U8941
結束頁: U8941
顯示於類別:會議論文


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