Browsing by Author "Wang, Mei-Tan"

Now showing 1 - 5 of 5

Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons
(2016-03-03)
Yao, Yung-Chi
;
Hwang, Jung-Min
;
Yang, Zu-Po
;
Haung, Jing-Yu
;
Lin, Chia-Ching
Enhancement of the external quantum efficiency of a GaN-based vertical-type light emitting diode (VLED) through the coupling of localized surface plasmon (LSP) resonance with the wave-guided mode light is studied. To achieve this experimentally, Ag nanoparticles (NPs), as the LSP resonant source, are drop-casted on the most top layer of waveguide channel, which is composed of hydrothermally synthesized ZnO nanorods capped on the top of GaN-based VLED. Enhanced light-output power and external quantum efficiency are observed, and the amount of enhancement remains steady with the increase of the injected currents. To understand the observations theoretically, the absorption spectra and the electric field distributions of the VLED with and without Ag NPs decorated on ZnO NRs are determined using the finite-difference time-domain (FDTD) method. The results prove that the observation of enhancement of the external quantum efficiency can be attributed to the creation of an extra escape channel for trapped light due to the coupling of the LSP with wave-guided mode light, by which the energy of wave-guided mode light can be transferred to the efficient light scattering center of the LSP.
Luminous efficiency enhancement of white light-emitting diodes by using a hybrid phosphor structure
(2015-02-19)
Lin, Bing-Cheng
;
Huang, Jhih-Kai
;
Chen, Kuo-Ju
;
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)
Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors
(2014-10-20)
Lee, Ya-Ju
;
Yang, Zu-Po
;
Chen, Pin-Guang
;
Hsieh, Yung-An
;
Yao, Yung-Chi
In this study, we report a novel monolithically integrated GaN-based light-emitting diode (LED) with metal-oxide-semiconductor field-effect transistor (MOSFET). Without additionally introducing complicated epitaxial structures for transistors, the MOSFET is directly fabricated on the exposed n-type GaN layer of the LED after dry etching, and serially connected to the LED through standard semiconductor-manufacturing technologies. Such monolithically integrated LED/MOSFET device is able to circumvent undesirable issues that might be faced by other kinds of integration schemes by growing a transistor on an LED or vice versa. For the performances of resulting device, our monolithically integrated LED/MOSFET device exhibits good characteristics in the modulation of gate voltage and good capability of driving injected current, which are essential for the important applications such as smart lighting, interconnection, and optical communication. (C) 2014 Optical Society of America
Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors: reply
(2018-01-22)
Lee, Ya-Ju
;
Yang, Zu-Po
;
Chen, Pin-Guang
;
Hsieh, Yung-An
;
Yao, Yung-Chi
We present some comments to the paper "Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors: comment" [Opt. Express 22, A1589 (2014)]. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Size-dependent lattice dynamics of barium titanate nanoparticles
(2007-11-28)
Huang, Tung-Ching
;
Wang, Mei-Tan
;
Sheu, Hwo-Shuenn
;
Hsieh, Wen-Feng
;
光電工程學系
By applying a single-tetragonal-phase model to refine the crystal structure and the coupled-phonon model to analyze transverse optical ( TO) modes of BaTiO3 nanocrystals, we found, upon decreasing the particle size from 140 to 30 nm, that the tetragonality of BaTiO3 nanocrystallites is reduced accompanied by expanding unit-cell volume, which is the dominant mechanism for reducing giant LO-TO splitting in the BaTiO3 system. The weakening coupling of two low-frequency modes among three A(1) ( TO) phonons leads to changing the lowest one from a spectral dip to a peak, whereas the increasing coupling strength between two high-frequency modes repels them farther so that there is less reduction in spectral separation.