Browsing by Author "Hu, Sheng-Yao"

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Effects of magnesium contents in ZnMgO ternary alloys grown by molecular beam epitaxy
(2015-07-05)
Hu, Sheng-Yao
;
Chou, Wu-Ching
;
Weng, Yu-Hsiang
;
電子物理學系
;
Department of Electrophysics
Ternary alloys of ZnMgO samples with different magnesium contents have been grown by molecular beam epitaxy on the sapphire substrates. Room temperature photoluminescence energy of ZnMgO shifted as high as 3.677 eV by increasing Mg contents corresponding to the higher Urbach average localization energy which indicates more randomness in the alloys with higher Mg contents. XRD results are also verified that the c-axis length decreases as the increasing Mg contents linking to the increased tensile stress produced by the Mg atoms. Raman spectra analyzed by the spatial correlation model to describe that the linewidth Gamma is decreased but the correlation length L is increased as the increasing of Mg contents. (C) 2015 Elsevier B.V. All rights reserved.
Investigation of omnidirectional reflection band in ZnTe/ZnSe distributed Bragg reflector
(2015-11-15)
Huang, Ying-Shin
;
Hu, Sheng-Yao
;
Lee, Yueh-Chien
;
Chang, Chung-Cheng
;
Tiong, Kwong-Kau
We report the characteristics of reflectance spectra of the 15- and 20-period ZnTe/ZnSe distributed Bragg reflector grown on GaAs (001) substrates by molecular beam epitaxy. The reflectance spectra measured at various incident angles and polarizations were investigated by the theoretical curves simulated using transfer matrix method. The wavelength variation of the refractive indices described by Sellmeier equation and random thickness model were also considered for the interpretation of the experimentally observed curves. An omnidirectional reflection range defined from the edge of incident-angle-dependent reflection band with TE and TM polarizations is about 15 nm, and is consistent with the observed experimental curves. The results showed that the selected ZnTe and ZnSe materials are suitable for constructing multilayer structures having omnidirectional reflection band. (C) 2015 Elsevier B.V. All rights reserved.