Browsing by Author "Hsu, S. C."

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A Stress Analysis of Transferred Thin-GaN Light-Emitting Diodes Fabricated by Au-Si Wafer Bonding
(2013-05-01)
Lin, Bo-Wen
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Wu, Nian-Jheng
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Wu, Yew Chung Sermon
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Hsu, S. C.
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材料科學與工程學系
Thin-GaN light-emitting diodes were fabricated by Au-Si wafer bonding and laser lift-off. The relaxation process of the thermal strain in the transferred GaN films on a Si substrate was studied by varying the bonding film thickness of the Au over a wide range from 7 mu m to 40 mu m. The transferred GaN films were found to be strained by the biaxial compressive stress. A 10 mu m Au bonding layer thickness was proven to have the lowest residual compressive stress, and the complete compressive stress variation throughout the entire thin-GaN fabrication process is discussed. Finally, we changed the biaxial in-plane stress of the transferred GaN thin film by controlling the bonding conditions, including the bonding layer thickness and the bonding temperature.
Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate
(2012-03-01)
Lin, H. Y.
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Chen, Y. J.
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Chang, C. L.
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Li, X. F.
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Kuo, C. H.
Chemical wet etching on c-plane sapphire wafers by three etching solutions (H3PO4, H2SO4, and H3PO4/H2SO4 mixing solution) was studied. Among these etching agents, the mixing H3PO4/H2SO4 solution has the fastest etching rate (1.5 mu m/min). Interestingly, we found that H2SO4 does not etch the c-plane sapphire wafer in thickness; instead, a facet pyramidal pattern is formed on the c-plane sapphire wafer. GaN light-emitting diode (LED) epitaxial structure was grown on the sapphire wafer with the pyramidal pattern and the standard flat sapphire wafer. X-ray diffraction and photoluminescence measurement show that the pyramidal pattern on the sapphire wafer improved crystalline quality but augmented the compressive stress level in the GaN LED epilayer. The horizontal LED chips fabricated on the pyramidal-patterned sapphire wafer have a larger light output than the horizontal LED chips fabricated on the standard flat sapphire wafer by 20%.
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.
Study on GaN micro-rod growth by nature patterned sapphire substrate
(2009)
Hsu, S. C.
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Tu, P. M.
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Chen, I. R.
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Cheng, Y. J.
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光電工程學系
In this study, we Investigated the kinetics and etched morphology on sapphire substrate by mixing acid solutions We developed different etching conditions to produce various etching morphology patterns on sapphire surface Then, GaN micro-rod embedded with quantum wells (QWs) were grown on the patterned sapphire surface The cathode luminescence (CL) images of these QW embedded micro-rods have shown great crystal quality.