Browsing by Author "Lin, Bo-Wen"

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A Stress Analysis of Transferred Thin-GaN Light-Emitting Diodes Fabricated by Au-Si Wafer Bonding
(2013-05-01)
Lin, Bo-Wen
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Wu, Nian-Jheng
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Wu, Yew Chung Sermon
;
Hsu, S. C.
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材料科學與工程學系
Thin-GaN light-emitting diodes were fabricated by Au-Si wafer bonding and laser lift-off. The relaxation process of the thermal strain in the transferred GaN films on a Si substrate was studied by varying the bonding film thickness of the Au over a wide range from 7 mu m to 40 mu m. The transferred GaN films were found to be strained by the biaxial compressive stress. A 10 mu m Au bonding layer thickness was proven to have the lowest residual compressive stress, and the complete compressive stress variation throughout the entire thin-GaN fabrication process is discussed. Finally, we changed the biaxial in-plane stress of the transferred GaN thin film by controlling the bonding conditions, including the bonding layer thickness and the bonding temperature.
Crystal Quality and Light Output Power of GaN-Based LEDs Grown on Concave Patterned Sapphire Substrate
(2015-04-01)
Wu, YewChung Sermon
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Isabel, A. Panimaya Selvi
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Zheng, Jian-Hsuan
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Lin, Bo-Wen
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Li, Jhen-Hong
The crystal quality and light output power of GaN-based light-emitting diodes (LEDs) grown on concave patterned sapphire substrate (CPSS) were investigated. It was found that the crystal quality of GaN-based LEDs grown on CPSS improved with the decrease of the pattern space (percentage of c-plane). However, when the pattern space decreased to 0.41 mu m (S0.41-GaN), the GaN crystallinity dropped. On the other hand, the light output power of GaN-based LEDs was increased with the decrease of the pattern space due to the change of the light extraction efficiency.
Enhanced Performance of LEDs Using Periodic Tent-Like Post Patterns on A-plane Sapphire Substrates
(2011-12-01)
Lin, Bo-Wen
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Chang, Chung-Cheng
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Hsieh, Cheng-Yu
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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
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Hsiao, Feng Ching
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Lin, Bo-Wen
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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.
High brightness III-V light-emitting diodes on diamond/silicon composite substrate
(2013)
Chang, Tai-min
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Hu, Jen-Li
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Lin, Bo-Wen
;
Wu, YewChung Sermon
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材料科學與工程學系
Thermal management of LED is currently an important issue because the increase of junction temperature degrades LED\'s performance and reliability. Replace that substrate to high thermal conductivity substrate can improved this problem. Diamond has the highest thermal conductivity (similar to 2000W/mK) in all material but is hard to process and has low reactivity with other material. In this study, high-brightness III-V light-emitting diodes on Si/diamond composite substrate can be fabricate by filled diamond particle into the blind-hole of the silicon substrate, wafer-bonding and lift-off process. In order to confirm that diamond particle provided a direct thermal path for heat dissipation, a simple sandwich structure was also been done.
Improved crystal quality and performance of GaN-based light-emitting diodes by decreasing the slanted angle of patterned sapphire
(2010-02-01)
Cheng, Ji-Hao
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Wu, YewChung Sermon
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Liao, Wei-Chih
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Lin, Bo-Wen
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材料科學與工程學系
Periodic triangle pyramidal array patterned sapphire substrates (PSSs) with various slanted angles were fabricated by wet etching. It was found beside normal wurtzite GaN, zinc blende GaN was found on the sidewall surfaces of PSS. The crystal quality and performance of PSS-LEDs improved with decrease in slanted angle from 57.4 degrees to 31.6 degrees. This is because most of the growth of GaN was initiated from c-planes. As the growth time increased, GaN epilayers on the bottom c-plane covered these pyramids by lateral growth causing the threading dislocation to bend toward the pyramids.
Improvement of Epitaxy GaN Quality Using Liquid-Phase Deposited Nano-Patterned Sapphire Substrates
(2012-12-15)
Hsieh, Cheng-Yu
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Lin, Bo-Wen
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Cho, Hsin-Ju
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Wang, Bau-Ming
;
Chang, Nancy
A relatively simple and easy and inexpensive liquid-phase deposition (LPD) method is employed to introduce nanoscale silica hemispheres on sapphire substrates for fabricating a nano-patterned sapphire substrate (NPSS). Compared with GaN grown on sapphire without any pattern, the NPSS-GaN film is of much better quality as observed by scanning electron microscopy, transmission electron-microscopy, X-ray diffraction, cathodoluminescence, and photoluminescence. This is because GaN is initiated from the c-plane instead of the LPD-silica surface. In addition, many dislocations within the NPSS-GaN bend toward the patterns, or end at the GaN/void interfaces.
Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs
(2014-11-03)
You, Yao-Hong
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Su, Vin-Cent
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Ho, Ti-En
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Lin, Bo-Wen
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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).
Investigation of GaN Films Grown on Liquid-Phase Deposited SiO2 Nanopatterned Sapphire Substrates
(2012)
Hsieh, Cheng-Yu
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Lin, Bo-Wen
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Cho, Hsin-Ju
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Wang, Bau-Ming
;
Wu, YewChung Sermon
A simple, easy and relatively inexpensive liquid phase deposition (LPD) method was used to introduce nano SiO2 on sapphire substrates to fabricate nanoscale patterned sapphire substrates (PSS). Two kinds of nanoscale PSS were used to grow GaN, namely "NPOS" which is nano-pattern oxide on sapphire substrate and "NPSS" which is nano-patterned sapphire substrate. It was found that upper region of NPSS-GaN had the best quality. This is because as the growth time increased, laterally-grown GaN caused the threading dislocations to bend toward the patterns. Besides, voids formed on the NPSS pattern sidewalls caused more threading dislocation bending toward these voids. (C) 2012 The Electrochemical Society. All rights reserved.
Light Extraction Enhancement of GaN-Based Light-Emitting Diodes Using Crown-Shaped Patterned Sapphire Substrates
(2012-07-15)
Chiu, Ching-Hsueh
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Hsu, Lung-Hsing
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Lee, Chia-Yu
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Lin, Chien-Chung
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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
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Lin, Bo-Wen
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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.
Multifacet Microrod Light-Emitting Diode With Full Visible Spectrum Emission
(2016-09)
Li, Yun-Jing
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Chang, Jet-Rung
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Chang, Shih-Pang
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Lin, Bo-Wen
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Yeh, Yen-Hsien
We demonstrated a full visible spectrum emission from a 3D multifacet microrod light-emitting diode (LED). The microrods were fabricated by top-down patterned etched and regrowth. Hexagonal {11-20} and {11-22} facets were first formed on the microrods, then gradually transformed to {10-10} and {10-11} facets. This facet evolution was attributed to the growth competition among different crystal planes. The multiple quantum wells grown on the microrods also followed this facet evolution and resulted in broad emission spectrum. The device can have direct white light emission covering full visible spectral range from 460 to 660 nm under electrical injection.
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
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Hsieh, Cheng-Yu
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Lin, Bo-Wen
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Cho, Hsin-Ju
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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.
Semipolar GaN Films on Prism Stripe Patterned a-Plane Sapphire Substrates
(2012)
Hsieh, Cheng-Yu
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Lin, Bo-Wen
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Cheng, Wen-Hao
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Wang, Bau-Ming
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Chang, Li
A (10 (1) over bar4) semipolar GaN layer was grown on periodic stripe patterned a-plane sapphire substrate fabricated by using two-steps etching process. The stripes in prism shape were inclined with sapphire c-axis in 60 degrees. The orientation relationship between semipolar GaN and sapphire is (0002)(GaN)//(2 (1) over bar(1) over bar(3) over bar)(sapphire) and [2 (1) over bar(1) over bar0](GaN)//[23 (5) over bar2](sapphire) as defined by selected area diffraction in transmission electron microscopy (TEM). Growth of semipolar GaN on the sidewalls of the prism stripes is evidenced from TEM and X-ray phi scan. The quality of semipolar GaN film is reasonably good as examined with X-ray rocking curves. In addition, TEM and cathodoluminescence results show that the dislocation density in the semipolar GaN is significantly reduced near the film surface. (C) 2012 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
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Hsiao, Feng-Ching
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Lin, Bo-Wen
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Wang, Bau-Ming
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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
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Lin, Bo-Wen
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Hsu, Wen-Ching
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Wu, YewChung Sermon
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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
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Niu, Chen-Yi
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Hsieh, Cheng-Yu
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Wang, Bau-Ming
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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.