Browsing by Author "Hsieh, Cheng-Yu"

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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.
Improvement of Epitaxy GaN Quality Using Liquid-Phase Deposited Nano-Patterned Sapphire Substrates
(2012-12-15)
Hsieh, Cheng-Yu
;
Lin, Bo-Wen
;
Cho, Hsin-Ju
;
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.
In Situ Investigation of Defect-Free Copper Nanowire Growth
(2018-02-01)
Lin, Ting-Yi
;
Chen, Yong-Long
;
Chang, Chia-Fu
;
Huang, Guan-Min
;
Huang, Chun-Wei
The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) nanowires, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu nanowire growth has been found to be important. Here, we report the synthesis of defect-free single-crystalline Cu nanowires by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop of an amorphous carbon (a-C) lacey film surface. Without a metal-catalyst or induced defects, the high quality Cu nanowires formed with high aspect ratio and high growth rate of 578 nm/s. The dynamic study of the growth of heterogeneous nanowires was conducted in situ with a high-resolution transmission electron microscope. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu nanowire on a-C lacey film.
Interface Morphology Investigation of Bonded p-GaAs/p-Si Wafers
(2010)
Hsieh, Cheng-Yu
;
YewChung
;
Wu, Sermon
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The integration of GaAs and Si can combine the superior electrical and optical properties of GaAs with the mechanical and economical advantages of Si. It presents great potential for OEICs applications. In this study, direct wafer bonding was applied to combine bulk p-Si and p-GaAs. Interface morphologies of bonded p-GaAs/p-Si wafers were investigated by TEM.
Investigation of GaN Films Grown on Liquid-Phase Deposited SiO2 Nanopatterned Sapphire Substrates
(2012)
Hsieh, Cheng-Yu
;
Lin, Bo-Wen
;
Cho, Hsin-Ju
;
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.
Observation of Resistive Switching Behavior in Crossbar Core-Shell Ni/NiO Nanowires Memristor
(2018-02-08)
Ting, Yi-Hsin
;
Chen, Jui-Yuan
;
Huang, Chun-Wei
;
Huang, Ting-Kai
;
Hsieh, Cheng-Yu
The crossbar structure of resistive random access memory (RRAM) is the most promising technology for the development of ultrahigh-density devices for future nonvolatile memory. However, only a few studies have focused on the switching phenomenon of crossbar RRAM in detail. The main purpose of this study is to understand the formation and disruption of the conductive filament occurring at the crossbar center by real-time transmission electron microscope observation. Core-shell Ni/NiO nanowires are utilized to form a cross-structure, which restrict the position of the conductive filament to the crosscenter. A significant morphological change can be observed near the crossbar center, which results from the out-diffusion and backfill of oxygen ions. Energy dispersive spectroscopy and electron energy loss spectroscopy demonstrate that the movement of the oxygen ions leads to the evolution of the conductive filament, followed by redox reactions. Moreover, the distinct reliability of the crossbar device is measured via ex situ experiments. In this work, the switching mechanism of the crossbar core-shell nanowire structure is beneficial to overcome the problem of nanoscale minimization. The experimental method shows high potential to fabricate high-density RRAM devices, which can be applied to 3D stacked package technology and neuromorphic computing systems.
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.
Semipolar GaN Films on Prism Stripe Patterned a-Plane Sapphire Substrates
(2012)
Hsieh, Cheng-Yu
;
Lin, Bo-Wen
;
Cheng, Wen-Hao
;
Wang, Bau-Ming
;
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.
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.