Browsing by Author "Cheng, Bo-Siao"

Now showing 1 - 11 of 11

Characteristics of an Electrically Pumped GaN-based Microcavity Light Emitter with an AlN Current Blocking Layer
(2012)
Cheng, Bo-Siao
;
Wu, Tzeng-Tsong
;
Lai, Ying-You
;
Wu, Yun-Lin
;
Chen, Cheng-Hung
We demonstrate a GaN-based microcavity light emitter (MCLE) with an AlN current blocking layer. An AlN layer is inserted on the InGaN/GaN multiple quantum wells as a current blocking layer and an optical confinement layer. (C)2011 Optical Society of America
Enhanced Light Extraction in Wafer-Bonded AlGaInP-Based Light-Emitting Diodes via Micro- and Nanoscale Surface Textured
(2009-10-01)
Lee, Yea-Chen
;
Kuo, Hao-Chung
;
Cheng, Bo-Siao
;
Lee, Chia-En
;
Chiu, Ching-Hua
AlGaInP-based metal-bonding light-emitting diodes (LEDs) with micro- and nanoscale textured surface were investigated. The device surface with microbowls and nanorods were formed by a chemical wet-etching and dry-etching technique for enhancing light-extraction purpose. The luminous intensity could be enhanced 65.8% under 20-mA current injection as compared with the plane surface LEDs. The maximum wall-plug efficiency was achieved 14.1% at 7.5-mA operation.
High Q microcavity light emitting diodes with buried AlN current apertures
(2011-07-25)
Cheng, Bo-Siao
;
Wu, Yun-Lin
;
Lu, Tien-Chang
;
Chiu, Ching-Hsueh
;
Chen, Cheng-Hung
We demonstrate a GaN-based high-Q microcavity light emitting diode (MCLED) with a buried AlN current aperture. A thin AlN layer is inserted on the InGaN/GaN multiple quantum wells as a current blocking layer and an optical confinement layer. The GaN-based MCLED is composed of a 29-pair GaN/AlN distributed Bragg reflector (DBR), an eight-pair of SiO(2)/Ta(2)O(5) dielectric DBR, and a three-lambda optical thickness InGaN/GaN active region. The current can be injected more effectively in the MCLED with a buried AlN current aperture. The output emission has a dominant emission peak wavelength at 440 nm with a very narrow linewidth of 0.52 nm, corresponding to a cavity Q-value of 846 at a driving current of 5 mA. (C) 2011 American Institute of Physics. [doi:10.1063/1.3617418]
High-performance 650 nm resonant-cavity light-emitting diodes for plastic optical-fiber application
(2007-04-01)
Lee, Yea-Chen
;
Lee, Chia-En
;
Cheng, Bo-Siao
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
AlGaInP-based resonant-cavity light-emitting diodes (RCLEDs) with high power and high speed have been fabricated. In this study, the RCLEDs were designed with different light-output aperture sizes 84, 60, and 40 pm, for different applications on plastic optical fibers. Small-signal modulation bandwidths as high as 3 10 MHz at a forward current of 20 mA and an output power as high as 1.5 mW can be achieved for devices with 40 pm apertures. The devices with 84 tm apertures had an output power of more than 3.5 mW at a driving current of 20 mA and a maximum efficiency of over 12% with an epoxy-encapsulated package. The devices with 40 mu m apertures satisfied with the IEEE 1394b s400 standard. Furthermore, the devices showed stable coupling efficiency for various currents and output powers at different ambience temperatures. In addition, the lifetime of devices is over 1300 h, and the power decay is less than 0.5 dB at 85 degrees C for a 40 mA driving current.
High-quality Quantum-Dot-Based Full-Color Display Technology by Pulsed Spray Method
(2013)
Chen, Kuo-Ju
;
Chen, Hsin-Chu
;
Tsai, Kai-An
;
Lin, Chien-Chung
;
Tsai, Hsin-Han
We fabricated the colloidal quantum-dot light-emitting diodes (QDLEDs) with the HfO2/SiO2-distributed Bragg reflector (DBR) structure using a pulsed spray coating method. Moreover, pixelated RGB arrays, 2-in. wafer-scale white light emission, and an integrated small footprint white light device were demonstrated. The experimental results showed that the intensity of red, blue, and green (RGB) emissions exhibited considerable enhancement because of the high reflectivity in the UV region by the DBR structure, which subsequently increased the use in the UV optical pumping of RGB QDs. In this experiment, a pulsed spray coating method was crucial in providing uniform RGB layers, and the polydimethylsiloxane (PDMS) film was used as the interface layer between each RGB color to avoid cross-contamination and self-assembly of QDs. Furthermore, the chromaticity coordinates of QDLEDs with the DBR structure remained constant under various pumping powers in the large area sample, whereas a larger shift toward high color temperatures was observed in the integrated device. The resulting color gamut of the proposed QDLEDs covered an area 1.2 times larger than that of the NTSC standard, which is favorable for the next generation of high-quality display technology.
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.
Light Output Enhancement of UV Light-Emitting Diodes With Embedded Distributed Bragg Reflector
(2011-05-15)
Cheng, Bo-Siao
;
Chiu, Ching-Hsueh
;
Lo, Ming-Hua
;
Wu, Yun-Lin
;
Kuo, Hao-Chung
We demonstrate the output power enhancement of ultraviolet light-emitting diodes (UVLEDs) by epitaxial lateral over-growth (ELOG) on a distributed Bragg reflector (DBR) patterned substrate. The patterned DBR mesas are used as ELOG masks to improve material quality as well as reflectors to enhance the light output coupling. Compared with the conventional UVLEDs, the surface pit density of UVLEDs at regions right above embedded patterned DBR were reduced from 2.5 x 10(6) to 1.6 x 10(6) cm(-2). The improved light extraction efficiency is verified by ray tracing simulation. The luminous intensity of this novel structure is enhanced by 75% compared to that of reference UVLED structure at the wavelength 390 nm.
Light Output Enhancement of UV Light-Emitting Diodes With Embedded Distributed Bragg Reflector
(2011-05-15)
Cheng, Bo-Siao
;
Chiu, Ching-Hsueh
;
Lo, Ming-Hua
;
Wu, Yun-Lin
;
Kuo, Hao-Chung
We demonstrate the output power enhancement of ultraviolet light-emitting diodes (UVLEDs) by epitaxial lateral over-growth (ELOG) on a distributed Bragg reflector (DBR) patterned substrate. The patterned DBR mesas are used as ELOG masks to improve material quality as well as reflectors to enhance the light output coupling. Compared with the conventional UVLEDs, the surface pit density of UVLEDs at regions right above embedded patterned DBR were reduced from 2.5 x 10(6) to 1.6 x 10(6) cm(-2). The improved light extraction efficiency is verified by ray tracing simulation. The luminous intensity of this novel structure is enhanced by 75% compared to that of reference UVLED structure at the wavelength 390 nm.
Power Enhancement of GaN-Based Flip-Chip Light-Emitting Diodes with Triple Roughened Surfaces
(2009-04-01)
Cheng, Bo-Siao
;
Lee, Chia-En
;
Kuo, Hao-Chung
;
Lu, Tien-Chang
;
Wang, Shing-Chung
The flip-chip light emitting diodes (FC-LEDs) with triple roughened surfaces were fabricated comprising top surface sapphire textured layer, interface patterned sapphire layer, and bottom naturally textured p-GaN layer. Light extraction efficiency was enhanced by such triple textured layers. The light output power of FC-LEDs was increased 60% (at 350 mA current injection) compared to that of conventional FC-LEDs by implementing the triple roughened surfaces. The enhancement efficiency can be simulated and the simulated results showed the same trend as the results of experiment. (C) 2009 The Japan Society of Applied Physics
Resonant-Enhanced Full-Color Emission of Quantum-Dot-Based Display Technology Using a Pulsed Spray Method
(2012-12-19)
Chen, Kuo-Ju
;
Chen, Hsin-Chu
;
Tsai, Kai-An
;
Lin, Chien-Chung
;
Tsai, Hsin-Han
Colloidal quantum-dot light-emitting diodes (QDLEDs) with the HfO2/SiO2-distributed Bragg reflector (DBR) structure are fabricated using a pulsed spray coating method. Pixelated RGB arrays, 2-in. wafer-scale white light emission, and an integrated small footprint white light device are demonstrated. The experimental results show that the intensity of red, green, and blue (RGB) emission exhibited considerable enhancement because of the high reflectivity in the UV region by the DBR structure, which subsequently increases the use in the UV optical pumping of RGB QDs. A pulsed spray coating method is crucial in providing uniform RGB layers, and the polydimethylsiloxane (PDMS) film is used as the interface layer between each RGB color to avoid cross-contamination and self-assembly of QDs. Furthermore, the chromaticity coordinates of QDLEDs with the DBR structure remain constant under various pumping powers in the large area sample, whereas a larger shift toward high color temperatures is observed in the integrated device. The resulting color gamut of the proposed QDLEDs covers an area 1.2 times larger than that of the NTSC standard, which is favorable for the next generation of high-quality display technology.
Temperature dependent gain characteristics in GaN-based vertical-cavity surface-emitting lasers
(2009-10-26)
Lu, Tien-Chang
;
Cheng, Bo-Siao
;
Liu, Mei-Chung
;
光電工程學系
;
Department of Photonics
Temperature dependent gain characteristics and linewidth enhancement factor (alpha-factor) of vertical-cavity surface-emitting lasers with InGaN/GaN multiple quantum wells were studied by measuring the photoluminescence spectra below the threshold condition and analyzed by using the Hakki-Paoli method. The optical gain and differential gain showed a more rapid increase as a function of the injected carriers as temperature decreased. The alpha-factor for the lasing mode was estimated as 2.8 at room temperature and decreased to a value as low as 0.6 at 80 K. (C) 2009 Optical Society of America