Browsing by Author "Lee, Chia-En"

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Directional light extraction enhancement from GaN-based film-transferred photonic crystal light-emitting diodes
(2009-03-23)
Lai, Chun-Feng
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Chao, Chia-Hsin
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Kuo, Hao-Chung
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Yen, His-Hsuan
;
Lee, Chia-En
Experimental investigation of the directionality in the far-field pattern and light extraction enhancement in collected cone were performed in GaN-based film-transferred photonic crystal (PhC) light-emitting diodes (FTLEDs). Angular-resolved measurement revealed directional profile and azimuthal anisotropy in the far-field distribution with guided modes extraction. Good agreement according to Bragg's diffraction theory and free photon band structure were achieved. The light enhancement in PhC FTLEDs compared to non-PhC FTLEDs within the collection cone angle was obtained according to measured three-dimensional far-field patterns. In a +/- 20 degrees collection cone, collected light was enhanced by a factor of similar to 2.4 for the collimated PhC FTLED.
Enhanced Light Extraction in Wafer-Bonded AlGaInP-Based Light-Emitting Diodes via Micro- and Nanoscale Surface Textured
(2009-10-01)
Lee, Yea-Chen
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Kuo, Hao-Chung
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Cheng, Bo-Siao
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Lee, Chia-En
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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.
Enhancement of flip-chip light-emitting diodes with omni-directional reflector and textured micropillar arrays
(2007-07-01)
Lee, Chia-En
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Lee, Yi-Jiun
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Kuo, Hao-Chung
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Tsai, Meng-Ru
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Cheng, B. S.
The flip-chip light-emitting diodes (FC-LEDs) with a conductive omni-directional reflector and textured micropillar arrays were investigated. The micropillar arrays structure was formed on the bottom side of sapphire substrate by dry etching process to increase the light-extraction efficiency. The light output power of the FC-LED was increased by 65% for a 3.2-mu m textured micropillar on the bottom side of the sapphire substrate. Our work offers promising potential for enhancing output powers of commercial light-emitting devices.
Enhancement of flip-chip light-emitting diodes with omni-directional reflector and textured micropillar arrays (vol 19, pg 18, 2007)
(2007-09-01)
Lee, Chia-En
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Lee, Yea-Chen
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Kuo, Hao-Chung
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Tsai, Meng-Ru
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Cheng, B. S.
Enhancing the light extraction of (AlxGa1-x)(0.5)In0.5P-based light-emitting diode fabricated via geometric sapphire shaping
(2008-03-01)
Lee, Yea-Chen
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Lee, Chia-En
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Kuo, Hao-Chung
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Lu, Tien-Chang
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Wang, Shing-Chung
AlGaInP-based light-emitting diodes (LEDs) with a transparent sapphire substrate were fabricated by. the glue-bonding (GB) method. This transparent sapphire substrate is a geometric shaping structure by wet etching processes. Furthermore, the n-side-up surface has a nano-roughened texture by natural mask and chemical wet etching processes. The light output of this novel LED structure could be enhanced about 26.7% (at 350 mA) due to the higher light extraction as compared with the conventional GB-LEDs.
Far-Field and Near-Field Distribution of GaN-Based Photonic Crystal LEDs With Guided Mode Extraction
(2009-07-01)
Lai, Chun-Feng
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Chi, Jim-Yong
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Kuo, Hao-Chung
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Yen, Hsi-Hsuan
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Lee, Chia-En
The near-field and far-field distribution of GaN LEDs with square photonic crystal (PhC) lattice are experimentally investigated. The optical images of the near-field pattern are obtained from the guided electroluminescent light generated at the center of a special annular structure. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The far-field distribution is studied with GaN-based film-transferred PhC LEDs with the thickness about 1500 nm. Angular-resolved measurements under electrical injection revealed guided modes extraction behavior and polarization based on the Bragg's diffraction with the PhC lattice. Good agreement with the two-dimension free photon band structure is obtained.
Far-field of GaN film-transferred green light-emitting diodes with two-dimensional photonic crystals
(2009-05-25)
Lai, Chun-Feng
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Chi, Jim-Yong
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Kuo, Hao-Chung
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Yen, Hsi-Hsuan
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Lee, Chia-En
Far-field distributions of GaN-based photonic crystal (PhC) film-transferred light-emitting diodes (FT-LEDs) were investigated. The thickness of the device is about 840 nm. The emission wavelength is around 520 nm. The PhC region is a square lattice with a/lambda around 0.5. Angular-resolved measurements in the Gamma-X and Gamma-M directions were made in the polarized-resolved manner. Guided mode extraction behavior in agreement with the two-dimensional free-photon band calculation was observed. In addition, the pseudo-TM behavior for the non-collinearly coupled modes was observed. The azimuthal-mapping of the angular-resolved spectra revealed the evolution of the collinearly and the non-collinearly coupled modes. Furthermore, the light enhancement of similar to 2.7x and the collimation angle about 102.3 degrees were achieved. (c) 2009 Optical Society of America
Further enhancement of nitride-based near-ultraviolet vertical-injection light-emitting diodes by adopting a roughened mesh-surface
(2008-05-01)
Lee, Chia-En
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Lee, Yea-Chen
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Kuo, Hao-Chung
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Lu, Tien-Chang
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Wang, Shing-Chung
In this letter, the nitride-based near-ultraviolet (NUV) vertical-injection light-emitting diodes (VLEDs) with roughened mesh-surface are proposed and demonstrated by a combination of pattern sapphire substrate, wafer bonding, laser lift-off, and chemical wet etching processes. With the help of adopting a roughened mesh-surface, the light-output power (at 350 mA) of the NUV-VLEDs could be further enhanced about 20% as compared with that of the conventional NUV-VLED.
GaN-based film-transferred light-emitting diodes with photonic crystal
(2009)
Lai, Chun-Feng
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Chi, Jim-Yong
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Chao, Chia-Hsin
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Lee, Chia-En
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Kuo, Hao-Chung
Experimental investigation of A-type and B-type guided modes was performed in GaN-based film-transferred photonic crystal light-emitting diodes. Good agreement with the band structure calculated in the limit of two-dimensional free photon was obtained. (C)2009 Optical Society of America
High-brightness InGaN-GaN flip-chip light-emitting diodes with triple-light scatteriny layers
(2008-03-01)
Lee, Chia-En
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Lee, Yea-Chen
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Kuo, Hao-Chung
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Lu, Tien-Chang
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Wang, Shing-Chung
The flip-chip light-emitting diodes (FC-LEDs) with triple-light scattering layers were investigated comprising a top surface sapphire textured layer, an interface patterned sapphire layer, and a bottom naturally textured p-GaN layer. Such triple-textured layers are useful for light extraction efficiency enhancement. 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-light scattering layers.
High-Performance (Al(x)Ga(1-x))(0.5)In(0.5)P-Based Flip-Chip Light-Emitting Diode With a Geometric Sapphire Shaping Structure
(2008-11-01)
Lee, Yea-Chen
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Kuo, Hao-Chung
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Lee, Chia-En
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Lu, Tien-Chang
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Wang, Shing-Chung
AlGaInP-based flip-chip light-emitting diodes (LEDs) with geometric sapphire shaping structures were fabricated by sapphire chemical etching and glue-bonded techniques. Furthermore, a nanoscale rough texture was applied on the epiwafer surface. This novel structure improved the output light power, wall-plug efficiency, and reliability. The output power of this structure was enhanced 31.2% under 350-mA current injection as compared with the conventional AlGaInP flip-chip LEDs.
High-Performance (AlxGa1-x)(0.5)In0.5P-Based Flip-Chip Light-Emitting Diode With a Geometric Sapphire Shaping Structure
(2008-11-01)
Lee, Yea-Chen
;
Kuo, Hao-Chung
;
Lee, Chia-En
;
Lu, Tien-Chang
;
Wang, Shing-Chung
AlGaInP-based flip-chip light-emitting diodes (LEDs) with geometric sapphire shaping structures were fabricated by sapphire chemical etching and glue-bonded techniques. Furthermore, a nanoscale rough texture was applied on the epiwafer surface. This novel structure improved the output light power, wall-plug efficiency, and reliability. The output power of this structure was enhanced 31.2% under 350-mA current injection as compared with the conventional AlGaInP flip-chip LEDs.
High-performance 650 nm resonant-cavity light-emitting diodes for plastic optical-fiber application
(2007-04-01)
Lee, Yea-Chen
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Lee, Chia-En
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Cheng, Bo-Siao
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Lu, Tien-Chang
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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.
Metal organic chemical vapor deposition growth of GaN-based light emitting diodes with naturally formed nano pyramids
(2008-04-01)
Chiu, Ching-Hua
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Lee, Chia-En
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Lo, Ming-Hua
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Huang, Hung-Wen
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Lu, Tien-Chang
GaN-based light-emitting diodes (LEDs) with naturally formed nano pyramids roughened surfaces grown by metal organic chemical vapor deposition (MOCVD) were demonstrated. In this study, Mg-treatment, a growth-.interruption step and a surface treatment using biscyclopentadienyl magnesium (CP(2)Mg), was performed to form the nano pyramids on the surface of a p-type cladding layer, and then a p-type contact layer was grown on the p-type cladding layer, so as to create a p-type contact layer with a rough surface. Assisted by the nano pyramids surface roughening process, the light output power of the LEDs reached 11.3 and 9.7 mW with 10 and 5 min Mg-treatment at a driving current of 20 mA. The light outputs were increased by 48 and 27%, respectively, compared with the results from the LED without Mg-treatment.
Nitride-Based Thin-Film Light-Emitting Diodes With Photonic Quasi-Crystal Surface
(2009-03-01)
Lee, Chia-En
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Lai, Chun-Feng
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Lee, Yea-Chen
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Kuo, Hao-Chung
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Lu, Tien-Chang
In this letter, the nitride-based thin-film light-emitting diodes (TFLEDs) with eight-fold photonic quasi-crystal (PQC) surfaces are proposed and demonstrated by a combination of wafer bonding, laser lift-off, and electron-beam lithography processes. By adopting a PQC surface, the light-output power (at 350 mA) of the PQC-TFLEDs exhibits 140% output power enhancement as compared with that of TFLEDs without a PQC surface.
Power Enhancement of GaN-Based Flip-Chip Light-Emitting Diodes with Triple Roughened Surfaces
(2009-04-01)
Cheng, Bo-Siao
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Lee, Chia-En
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Kuo, Hao-Chung
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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