Infrared reflectance of optical phonon modes in AlGaN epitaxial layers grown on sapphire substrates

Jun-Rong Chen; Tien-Chang Lu; Gen-Sheng Huang; Tsung-Shine Ko; Hao-Chung Kuo; Shing-Chung Wang

doi:10.1117/12.760296

15 February 2008 Infrared reflectance of optical phonon modes in AlGaN epitaxial layers grown on sapphire substrates

Jun-Rong Chen, Tien-Chang Lu, Gen-Sheng Huang, Tsung-Shine Ko, Hao-Chung Kuo, Shing-Chung Wang

Proceedings Volume 6894, Gallium Nitride Materials and Devices III; 68941U (2008) https://doi.org/10.1117/12.760296
Event: Integrated Optoelectronic Devices 2008, 2008, San Jose, California, United States

Abstract

We reported the systematical study of optical properties of hexagonal Al_xGa_1-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 Al_xGa_1-xN varies between 4.98 and 4.52 for ε_∞⊥(polarization perpendicular to the optical axis) and between 4.95 and 4.50 for ε_∞,//(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 Al_xGa_1-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.

Citation Download Citation

Jun-Rong Chen, Tien-Chang Lu, Gen-Sheng Huang, Tsung-Shine Ko, Hao-Chung Kuo, and Shing-Chung Wang "Infrared reflectance of optical phonon modes in AlGaN epitaxial layers grown on sapphire substrates", Proc. SPIE 6894, Gallium Nitride Materials and Devices III, 68941U (15 February 2008); https://doi.org/10.1117/12.760296

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available