Browsing by Author "Zan, H. W."

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High efficiency light emitting diode with anisotropically etched GaN-sapphire interface
(2009-07-27)
Lo, M. H.
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Tu, P. M.
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Wang, C. H.
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Hung, C. W.
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Hsu, S. C.
We report the fabrication and study of high efficiency ultraviolet light emitting diodes with inverted micropyramid structures at GaN-sapphire interface. The micropyramid structures were created by anisotropic chemical wet etching. The pyramid structures have significantly enhanced the light output efficiency and at the same time also improved the crystal quality by partially relieving the strain and reducing the dislocation defects in GaN. The electroluminescent output power at normal direction was enhanced by 120% at 20 mA injection current and the output power integrated over all directions was enhanced by 85% compared to a reference sample.
Influence of Hydrogen on the Germanium Incorporation in a-Si1-xGex:H for Thin-Film Solar Cell Application
(2010-01-01)
Wang, C. M.
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Huang, Y. T.
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Yen, K. H.
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Hsu, H. J.
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Hsu, C. H.
In this work, we examined the Ge incorporation and the accompanied defect formation during PECVD deposition of hydrogenated amorphous silicon-germanium alloys (a-Si1-xGex:H). In particular, we studied the effect of hydrogen on film growth, defect formation, Ge and Si incorporation efficiencies, and the H-bonding configuration. Our results indicate that hydrogen has a strong effect on improving the a-Si1-xGex:H film quality and the Ge incorporation in a-Si1-xGex:H. With adequate hydrogen dilution, the a-Si1-xGex:H thin-film quality significantly improved. However, excessive hydrogen dilution degraded the film properties. A number of analytical tools were employed, including FTIR, XPS, UV-Visible spectroscopy, photoconductivity, etc. The a-Si1-xGex:H material having 24% Ge content and a bangap of 1.61ev produced the solar cell with a conversion efficiency of 7.07%.
Investigation of Cat-CVD amorphous silicon film properties under high catalyzer temperature
(2010)
Yen, K. H.
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Nishizaki, S.
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Ohdaira, K.
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Matsumura, H.
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Huang, Y. T.
In this study, we investigated the a-Si films which were deposited by Cat-CVD in the higher catalyzer temperature (T(cat)) regime. We studied the influence of high T(cat) on amorphous silicon (a-Si:H) thin-film properties. The information on a-Si-H bonding configuration was obtained by Fourier Transform Infrared Spectroscopy (FTIR). The film defect density was investigated by the electron spin resonance (ESR) as a function of T(cat), the distance between catalyzer and substrate (D(cs)), and the deposition pressure (P). (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Study of Crystallinity in mu c-Si: H Films Deposited by Cat-CVD for Thin Film Solar Cell Applications
(2010-01-01)
Hsu, C. H.
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Hsu, Y. P.
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Yao, F. H.
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Huang, Y. T.
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Tsai, C. C.
The crystallinity of the hydrogenated microcrystalline silicon (mu c-Si:H) film was known to influence the solar cell efficiency greatly. Also hydrogen was found to play a critical role in controlling the crystallinity. Instead of employing conventional plasma deposition techniques, this work focused on using catalytic chemical vapor deposition (Cat-CVD) to study the effect of hydrogen dilution and the filament-to-substrate distance on the crystallinity, deposition rate, microstructure factor and electrical property of the mu c-Si: H film. We found that the substrate material and structure can affect the crystallinity of the mu c-Si: H film and the incubation effect. Comparing bare glass, TCO-coated glass, a-Si: H-coated glass and mu c-Si: H-coated glass, the microcrystalline phase grows the fastest onto mu c-Si: H surface, but the slowest onto a-Si: H surface. Surprisingly, the template effect lasted for more than a thousand atomic layers of silicon.