Browsing by Author "Chu, Jung-Tang"

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Emission Characteristics of InGaN/GaN Vertical-Cavity Surface-Emitting Lasers
(2007)
Chu, Jung-Tang
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Lu, Tien-chang
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Kuo, Hao-Chung
;
Wang, Shing-Chung
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光電工程學系
Lasing characteristics of optically pumped GaN-based vertical-cavity surface-emitting lasers were investigated. The laser emission showed single and multiple spots emission patterns with spectral and spatial variation under different pumping conditions. (C) 2007 Optical Society of America
Emission characteristics of optically pumped GaN-based vertical-cavity surface-emitting lasers
(2006-09-18)
Chu, Jung-Tang
;
Lu, Tien-Chang
;
You, Min
;
Su, Bor-Jye
;
Kao, Chih-Chiang
The laser emission characteristics of a GaN-based vertical-cavity surface-emitting laser with two dielectric distributed Bragg reflectors were investigated under optically pumped operation at room temperature. The laser emitted wavelength at 415.9 nm with an emission linewidth of 0.25 nm and threshold pumping energy of 270 nJ. The laser has a high characteristic temperature of about 278 K and high spontaneous emission coupling factor of 10(-2). The laser emission showed single and multiple spot emission patterns with spectral and spatial variations under different pumping conditions. (c) 2006 American Institute of Physics.
GaN-based high-Q vertical-cavity light-emitting diodes
(2007-10-01)
Lu, Tien-Chang
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Kao, Tsung-Ting
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Kao, Chih-Chiang
;
Chu, Jung-Tang
;
Yeh, Kang-Fan
We report a fabrication and demonstration of a GaN-based high-Q vertical-cavity light-emitting diode (VCLED). The GaN VCLED is composed of a 25-pair high-reflectivity (98%) GaN/AlN distributed Bragg reflector (DBR), an eight-pair SiO2/Ta2O5 dielectric DBR (99%), and a three-A optical thickness InGaN/GaN active region. It shows a very narrow linewidth of 0.52 nm, corresponding to a cavity Q-value of 895 at a driving current of 10 mA and a dominant emission peak wavelength at 465.3 nm. In addition, this VCLED emission linewidth continues to decrease with an increasing injection current, suggesting a possible realization of GaN-based vertical-cavity surface emitting lasers.
Investigation of InGaN/GaN light emitting diodes with nano-roughened surface by excimer laser etching method
(2007-01-25)
Huang, Hung-Wen
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Kao, Chih-Chiang
;
Chu, Jung-Tang
;
Wang, Wei-Chih
;
Lu, Tien-Chang
The InGaN/GaN light emitting diodes (LEDs) with a nano-roughened top p-GaN surface fabricated by using Ni nano-masks and laser etching methods were demonstrated and analyzed. The experiment results observed the maximum light output power of the InGaN/GaN LED with a nano-roughened top p-GaN surface etched with the laser energy of 300 mJ/cm(2) was 1.55 times higher than that of a conventional LED, and the wall-plug efficiency was enhanced 68% at 20 mA. The series resistance of InGaN/GaN LED was reduced by 32% by the increase in the contact area of the nano-roughened surface. (c) 2006 Elsevier B.V. All rights reserved.
Lasing Behavior, Gain Property, and Strong Coupling Effects in GaN-Based Vertical-Cavity Surface-Emitting Lasers
(2008-08-01)
Lu, Tien-Chang
;
Chu, Jung-Tang
;
Chen, Shih-Wei
;
Cheng, Bo-Siao
;
Kuo, Hao-Chung
The optical properties of a GaN-based vertical-cavity surface-emitting laser (VCSEL) with two dielectric distributed Bragg reflectors were investigated under optically pumped operation. The laser emits blue-violet light at a wavelength of 414 nm at room temperature with a high spontaneous emission coupling factor (beta-factor) of 2 x 10(-2) and a linewidth of 0.25 nm. The optical gain was determined by the Hakki-Paoli method by measuring the photoluminescence spectra below threshold conditions. At room temperature, an optical gain of 2900 cm(-1) was obtained under threshold condition. The linewidth enhancement factor (alpha-factor) is estimated front the ratio of the wavelength and gain derivation with respect to the carrier density, and the alpha-factor at room temperature is estimated to be 2.8. Strong exciton-photon coupling in the microcavity was observed at room temperature. A 9 meV Rabi splitting with 60% peak-to-valley contrast was determined from the photoluminescence measurements. Emission spectra showing the evolution of anticrossing behavior were also observed.
Strong ultraviolet emission from InGaN/AlGaN multiple quantum well grown by multi-step process
(2007-04-01)
Chen, Hou-Guang
;
Hsu, Nai-Fang
;
Chu, Jung-Tang
;
Yao, Hsin-Hung
;
Lu, Tien-Chang
We propose a method of realizing strong ultraviolet emission from InGaN/AlGaN multiple quantum wells (MQWs) grown by a multi-step process. During growth of the quantum well layer, only trimethylindium (TMIn) and ammonia were introduced into the reactor, followed by a growth interruption treatment before growth of AlGaN barriers. The growth temperature of QWs dominates the photoluminescence (PL) emission peak position and surface morphologies of the films. It was found that the PL spectra of the samples with MQWs grown at 685 degrees C showed a strong UV emission at 380 nm. The correlation between surface structures and optical characteristics was studied by cathodoluminescence microscopy. The electroluminescence spectra under various injection currents showed a weak carrier localization effect induced by a quantum-confined Stark effect in the MQW.