Browsing by Author "Hsu, Wen-Ching"

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Enhanced Extraction and Efficiency of Blue Light-Emitting Diodes Prepared Using Two-Step-Etched Patterned Sapphire Substrates
(2009)
Lin, Ray-Ming
;
Lu, Yuan-Chieh
;
Yu, Sheng-Fu
;
Wu, YewChung Sermon
;
Chiang, Chung-Hao
Using a hot acid wet etching method, we have fabricated two types of patterned sapphire substrates: A pyramidal patterned sapphire substrate (PPSS) and a flat-top patterned sapphire substrate (FTPSS). After placing these samples into an atmospheric pressure metallorganic chemical vapor deposition system, we deposited standard InGaN light-emitting diode (LED) structures onto their surfaces. The crystal quality of these two surfaces was enhanced, as evidenced using X-ray diffraction (the full width at half-maximum decreased from 406.8 arcsec for the conventional sapphire to 356.4 and 349.2 arcsec for the PPSS and FTPSS samples, respectively). The output power of InGaN-based blue LEDs incorporating the PPSS and FTPSS improved to 17.9 and 18.7%, respectively, at 20 mA. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3231502] All rights reserved.
Enhanced Performance of LEDs Using Periodic Tent-Like Post Patterns on A-plane Sapphire Substrates
(2011-12-01)
Lin, Bo-Wen
;
Chang, Chung-Cheng
;
Hsieh, Cheng-Yu
;
Wang, Bau-Ming
;
Wu, YewChung Sermon
Periodic tent-like post patterns on a-plane sapphire substrates were fabricated using a two-step etching process. They were denoted as a-plane dot pattern sapphire substrate (ADPSS). Compared with the GaN-based light-emitting diode (LED) grown on a-plane sapphire without any pattern (AFlat), the ADPSS-LED has higher output power, light extraction efficiency (LEE), and external quantum efficiency (EQE), and better crystal quality. The output power of ADPSS-LED was 9.6 mW, which was 68.4% larger than the AFlat-LED. In addition, the blue shift of ADPSS-LED was found to be less than that of AFlat-LED.
Evolution of Bottom c-Plane on Wet-Etched Patterned Sapphire Substrate
(2013)
Chen, Chien-Chih
;
Hsiao, Feng Ching
;
Lin, Bo-Wen
;
Hsu, Wen-Ching
;
Wu, YewChung Sermon
Wet-etched pattern sapphire substrate (PSS) has been employed to improve the epitaxy of GaN-based LEDs. It was found that the crystal quality and performance of LEDs improved with decrease in c-plane areas of PSS. However, further decrease in bottom c-plane areas makes epitaxy of GaN film very difficult. In this research, the evolution of bottom c-plane was investigated through a systematic study. It was found that epitaxy difficulty might be due to the appearance of 6C facets {4 (1) over bar(3) over bar 18} and the disappearance of bottom c-plane. (C) 2013 The Electrochemical Society.
Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs
(2014-11-03)
You, Yao-Hong
;
Su, Vin-Cent
;
Ho, Ti-En
;
Lin, Bo-Wen
;
Lee, Ming-Lun
This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain. Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).
Light Extraction Enhancement of GaN-Based Light-Emitting Diodes Using Crown-Shaped Patterned Sapphire Substrates
(2012-07-15)
Chiu, Ching-Hsueh
;
Hsu, Lung-Hsing
;
Lee, Chia-Yu
;
Lin, Chien-Chung
;
Lin, Bo-Wen
In this letter, we report the high performance GaN-based light-emitting diodes (LEDs) with embedded air void array grown by metal-organic chemical vapor deposition. The donut-shaped air void was formed at the interface between crown-shaped patterned sapphire substrates (CPSS) and the GaN epilayer by conventional photolithography. The transmission electron microscopy images demonstrate that the threading dislocations were significantly suppressed by epitaxial lateral overgrowth (ELOG). The Monte Carlo ray-tracing simulation reveals that the light extraction of the air-voids embedded LED was dramatically increased due to a strong light reflection and redirection by the air voids.
Morphologies and plane indices of pyramid patterns on wet-etched patterned sapphire substrate
(2014-03-01)
Chen, Yu-Chung
;
Lin, Bo-Wen
;
Hsu, Wen-Ching
;
Wu, YewChung Sermon
;
材料科學與工程學系
A wet etching process was employed to investigate the evolution of pyramids on the patterned sapphire substrate (PSS). It has been found that the PSS comprised a hexagonal pyramid covered with six facets {3 (4) over bar 1 7} when disk-shaped SiO2 mask still remained. Three facets {1 (1) over bar 0 5} were exposed when mask was etched away. In this study, a continuous etching process was performed. It was found that another six facets {4 (5) over bar 1 30} and another three facets {1 (1) over bar 0 10} appeared on the bottom and the top of pyramid. Finally, when the etching time reached around 5 min, most of pyramids on the PSS disappeared. (C) 2013 Elsevier B.V. All rights reserved.
Reduced Residual Stress and Enhanced Performance of GaN-Based LEDs Prepared by Liquid Phase Deposition Silicon Oxide-Nano Patterned Sapphire Substrate
(2014-01-01)
Chang, Sheng-Chieh
;
Hsieh, Cheng-Yu
;
Lin, Bo-Wen
;
Cho, Hsin-Ju
;
Hsu, Wen-Ching
A simple liquid phase deposition (LPD) method was used to introduce nano SiO2 on sapphire substrates to fabricate nano-patterned sapphire substrates with top oxide layers (MNPSS). The X-ray diffraction (XRD) rocking curves and etching pit density (EPD) analyses show that the quality of MNPSS-GaN was better than that of GaN grown on flat sapphire substrates (FLAT-GaN). The photoluminescence (PL) spectrums showed a blueshift of MNPSS-GaN peak position compared with FLAT-GaN. The analyses of XRD reciprocal space map (RSM) revealed that this shift was caused by the residual stress. (C) 2014 The Electrochemical Society. All rights reserved.
The Formation and the Plane Indices of Etched Facets of Wet Etching Patterned Sapphire Substrate
(2012)
Chen, Yu-Chung
;
Hsiao, Feng-Ching
;
Lin, Bo-Wen
;
Wang, Bau-Ming
;
Wu, YewChung Sermon
A two-step chemical wet etching processes were used to investigated the formation and the plane indexes of exposed etched facets of wet etching patterned sapphire substrate (PSS). It was found when SiO2 mask still remained on the top c-plane, the structure of PSS comprised of a hexagonal pyramid covered with six facets {3 (4) over bar 17} with a flat top c-plane. When SiO2 mask were etched away, beside six facets on the bottom, there were 3 extra facets {1 (1) over bar 05} exposed on the top. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.095206jes] All rights reserved.
The Formation of Smooth Facets on Wet-Etched Patterned Sapphire Substrate
(2014)
Chen, Yu-Chung
;
Lin, Bo-Wen
;
Hsu, Wen-Ching
;
Wu, YewChung Sermon
;
材料科學與工程學系
In this study, rectangle-shaped SiO2 hard masks with various orientations were employed to find various facets on wet-etched patterned sapphire substrate (PSS). Seven facets (A, B, B-1, B-2, D-1, D-2 and E) were observed after etching. The surfaces of A, B and E-facets were smooth. Their plane indexes were {13 (4) over bar7}, {10 (1) over bar4} and {12 (3) over bar5}, respectively. On the other hand, the surfaces of B-1, B-2, D-1 and D-2-facets were not smooth, with some ambiguous stripes, which were investigated by using "zigzag triangle" hard mask. A large triangle-mask was employed to investigate smooth facets and the GaN epitaxial behavior. It was found that most of the growth of zincblende GaN was initiated not from A and B-facets but E-facets. (C) 2013 The Electrochemical Society. All rights reserved.
Using BCl3-Based Plasma to Modify Wet-Etching Pattern Sapphire Substrate for Improving the Growth of GaN-Based LEDs
(2013-02-15)
Lin, Bo-Wen
;
Niu, Chen-Yi
;
Hsieh, Cheng-Yu
;
Wang, Bau-Ming
;
Hsu, Wen-Ching
Wet-etching pattern sapphire substrates (PSS) have been used to grow GaN-based light-emitting diodes (LEDs). However, after wet etching, several sidewall facets are exposed on the patterns of PSS. These sidewall facets would grow zincblende GaN and form irregular voids. In this letter, BCl3-based plasma is used to solve this problem and improve the performance of GaN-based LEDs.