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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Shih, Min-HsiungSubject: search.filters.subject.GaN

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Now showing 1 - 7 of 7
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    Luminous efficiency enhancement of white light-emitting diodes by using a hybrid phosphor structure
    (2015-02-19)
    Lin, Bing-Cheng
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    Huang, Jhih-Kai
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    Chen, Kuo-Ju
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    Chiu, Sheng-Huan
    ;
    Tu, Zong-Yi
    This paper presents a "hybrid" structure for the coating of yellow YAG: Ce3(+) phosphor on blue GaN-based light-emitting diodes (LEDs). The luminous efficiency of the hybrid phosphor structure improved by 5.9% and 11.7%, compared with the conventional remote and conformal phosphor structures, respectively, because of the increased intensity of the yellow component. The hybrid structure also has an advantage in the phosphor usage reduction for the LEDs. Furthermore, the electric intensity of the hybrid phosphor structure was calculated for various thicknesses by conducting TFCalc32 simulation, and the enhanced utilization of blue rays was verified. Finally, the experimental results were consistent with the simulation results performed using the Monte-Carlo method. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Room temperature lasing characteristics in metal-coated GaN spiral and grating structures
    (2014)
    Liao, Wei-Chun
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    Liao, Shu-Wei
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    Chen, Kuo-Ju
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    Shih, Min-Hsiung
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    Kuo, Hao-Chung
    We had investigated a metal-coated GaN spiral structure laser at room temperature. The lasing action was observed around 363 nm wavelength with a low threshold power density. We also compare the lasing characteristics from metal-coated GaN spiral and grating structures. The experiment results ensure the circular-polarized emission from the metal-coated GaN spiral laser.
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    Wide-Range Correlated Color Temperature Light Generation From Resonant Cavity Hybrid Quantum Dot Light-Emitting Diodes
    (2015-07-01)
    Chen, Kuo-Ju
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    Lin, Chien-Chung
    ;
    Han, Hau-Vei
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    Lee, Chia-Yu
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    Chien, Shih-Hsuan
    This study presents extremely uniform colloidal quantum dot white light-emitting diodes (QD-WLEDs) that demonstrate a high color rendering index (CRI) and correlated color temperatures (CCTs) ranging from 2500 to 4500 K. Experimental results indicate that the structure of the distributed Bragg reflector (DBR) containing a stopband in the UV region enhances the intensity output of both monochromatic QD-LEDs and QD-WLEDs by reflecting the unconverted UV light back onto the package to excite the QDs further. Furthermore, the angular CCT uniformity of the QD-WLEDs also improved considerably because of the dependence of the DBR structure on the incident angle. The angular CCT deviation in the range of -70 degrees to 70 degrees decreased to 39 K and the CRI of the WLED is higher than 90. The high-CRI and uniform angular CCT QD-WLED containing the DBR demonstrates potential applicability as the lighting source of next-generation display devices and solid-state lighting.
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    Investigation and Comparison of the GaN-Based Light-Emitting Diodes Grown on High Aspect Ratio Nano-Cone and General Micro-Cone Patterned Sapphire Substrate
    (2013-12-01)
    Huang, Jhih-Kai
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    Lin, Da-Wei
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    Shih, Min-Hsiung
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    Lee, Kang-Yuan
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    Chen, Jyun-Rong
    In this paper, we demonstrated the high performance GaN-based LEDs by using a high aspect ratio cone-shape nano-patterned sapphire substrate (HAR-NPSS). We utilized nano-imprint lithography (NIL) and dry-etching system to fabricate a high depth HAR-NPSS. The micro-scale patterned sapphire substrate (PSS) was also used for comparison. A great enhancement of light output was observed when GaN-based LEDs were grown on a HAR-NPSS or a PSS. The light output power of LEDs with a HAR-NPSS and LEDs with a PSS were enhanced of 49 and 38% compared to LEDs with a unpatterned sapphire substrate. The high output power of the LED with a HAR-NPSS indicated that the technology of NAR-NPSS not only can improve the crystalline quality of GaN-based LEDs but also a promising development to a NPSS.
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    An Investigation of the Optical Analysis in White Light-Emitting Diodes With Conformal and Remote Phosphor Structure
    (2013-11-01)
    Chen, Kuo-Ju
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    Chen, Hsin-Chu
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    Lin, Chien-Chung
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    Wang, Chao-Hsun
    ;
    Yeh, Chia-Chi
    An effective emission model of phosphor film is proposed by using bidirectional scattering distribution function system (BSDF), and the model is verified by white light-emitting diodes (LEDs) with conformal and remote phosphor structure. The emission model is built to clarify the optical characteristics by analyzing the angular-dependent distribution of emission and excitation behaviors in phosphor film. The white LEDs with conformal and remote phosphor structure are also fabricated for experimental comparison. The uniformity of angular correlated color temperature (CCT) in white LEDs can be determined by the angular distribution of blue and yellow light, which is in turns decided by the refractive index variation between chip a (c) nd phosphor layers. Finally, the experimental results are found to have good agreement with the simulation results performing by the Monte Carlo method.
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    Enhanced Luminous Efficiency of WLEDs Using a Dual-Layer Structure of the Remote Phosphor Package
    (2013-06-15)
    Chen, Kuo-Ju
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    Chen, Hsin-Chu
    ;
    Shih, Min-Hsiung
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    Wang, Chao-Hsun
    ;
    Tsai, Hsin-Han
    This study demonstrates how the insertion of a thin silicone layer into a dual-layer remote phosphor structure enhances light extraction in white light-emitting diodes (WLEDs). In the experiment, a dual-layer phosphor structure yielded a higher intensity of blue and yellow components than a conventional structure. Moreover, the lumen flux was 5% higher than a conventional remote phosphor package at the same correlated color temperature (CCT). Using a TFCalc32 simulation, the electric field intensity was calculated for different thicknesses of the dual-layer remote phosphor structures, and the enhanced use of blue rays was verified. Additionally, the dual-layer structure reduces chromaticity deviations as the driving current increases.
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    The Influence of the Thermal Effect on CdSe/ZnS Quantum Dots in Light-Emitting Diodes
    (2012-07-15)
    Chen, Kuo-Ju
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    Chen, Hsin-Chu
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    Shih, Min-Hsiung
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    Wang, Chao-Hsun
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    Kuo, Ming-Yen
    This study investigates the effect of temperature on CdSe/ZnS quantum dots (QDs) in GaN-based light-emitting diodes (LEDs) using the phosphor conversion efficiency (PCE) and LED junction temperature. In our simulation, the blue chip and CdSe/ZnS QDs temperature are similar because of their minimal thickness. Furthermore, to verify the effect of temperature on CdSe/ZnS QDs, we use continuous wave and pulsed current sources to measure the relationship between the temperature and relative PCE. Higher junction temperatures are observed with greater CdSe/ZnS QD volume in LEDs. This is attributed to the thermal conduction and nonradiative energy between CdSe/ZnS QDs and blue chip. Therefore, if thermal management is improved, CdSe/ZnS QDs are expected to be used as color converting material in LEDs.