Browsing by Author "Cheng, Yuh-Jen"

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A Single InN Nanopillar Photodetector with Extended Infrared Response Grown by MOCVD
(2016)
Hsu, Lung-Hsing
;
Kuo, Chien-Ting
;
Cheng, Yuh-Jen
;
Chen, Kuan-Chao
;
Kuo, Hao-Chung
An extended infrared photoresponse is observed in a high quality InN pillar/p-GaN photodetector with self-assembly epitaxy grown by LP-MOCVD. The IR portion photocurrent as high as 14.2% can be measured via AM1.5G solar simulated spectra.
A ZnO/InN/GaN Heterojunction Photodetector with Extended Infrared Response
(2015)
Hsu, Lung-Hsing
;
Hsu, Shun-Chieh
;
Lee, Hsin-Ying
;
Tsai, Yu-Lin
;
Lin, Da-Wei
An extended infrared photoresponse is observed in a ZnO/InN/GaN heterojunction diode with InN grown by MOCVD. The external quantum efficiency is measured between 1200 and 1800 nm and can be as high as 3.55%.
An Investigation on Stable and Continuous Operation of Hybrid Perovskite Quantum Dot Light Emitting Diodes
(2019-01-01)
Cho, Yu-Yun
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Hsu, Shun-Chieh
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Huang, Yu-Ming
;
Shih, Hsiang-Yun
;
Lee, Ting-Yu
Two different package structures of hybrid perovskite quantum dots light emitting diodes were demonstrated with stable and continuous light emission. With boron nitride nanoparticles, the lifetime of device is expected to be thousands of hours.
Annealed Polycrystalline TiO2 Interlayer of the n-Si/TiO2/Ni Photoanode for Efficient Photoelectrochemical Water Splitting
(2020-04-27)
Chuang, Chi-Huang
;
Lai, Yung-Yu
;
Hou, Cheng-Hung
;
Cheng, Yuh-Jen
;
材料科學與工程學系
High photovoltage generation from a photoelectrode is important for efficient solar-driven water splitting. Here, we report a thermal treatment process that greatly enhances photovoltage generation from an n-Si/TiO2/Ni photoanode. By selectively annealing the TiO2 interlayer, the photoanode generates a high photovoltage of 570 mV, which is very competitive as compared with photovoltages produced using other similar metal-insulator-semiconductor structures with earth-abundant metal catalysts. Different annealing conditions and junction layer thicknesses were systematically investigated. It is found that the optimal annealing temperature occurs between 500 and 600 degrees C. Within this temperature range, the deposited amorphous Ti is converted into polycrystalline anatase phase TiO2. The optimal annealing time scales linearly with TiO2 thickness and inversely with annealing temperature. The large photovoltage generation is attributed to the reduced defect states and improved junction barrier height by the annealed TiO2 interlayer. This study demonstrates that thermal annealing offers an attractive approach to modify the TiO2 interlayer material's properties for photovoltage optimization.
Coreshell InGaN/GaN MQW Nanorod Photovoltaic Device
(2015)
Li, Yun-Jing
;
Tsai, Yu Lin
;
Chang, Jet-Rung
;
Chang, Shih-Pang
;
Lin, Chien-Chung
We report the fabrication and study of coreshell InGaN/GaN multiple quantum well (MQW) nanorod photovoltaic device. The nanorods were fabricated from a GaN substrate by top-down etch, followed by InGaN/GaN MQW growth. The 3D geometry allows higher Indium incorporation and extends the solar absorption spectral range as compared with a planar reference sample. The proof-of-concept coreshell nanorod photovoltaic device has a fill factor of about 54.2%, the short current density of 1.16 mA/cm(2), the open circuit voltage of 0.68 V, and the power conversion efficiency of 0.38%, respectively.
Deep-Ultraviolet Hyperbolic Metacavity Laser
(2018-05-24)
Shen, Kun-Ching
;
Ku, Chen-Ta
;
Hsieh, Chiieh
;
Kuo, Hao-Chung
;
Cheng, Yuh-Jen
Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.
Effect of Sputtered AlN Location on the Growth Mechanism of GaN
(2017-01-01)
Wu, Pei-Yu
;
Li, Jhen-Hong
;
Hsu, Lung-Hsing
;
Huang, Chia-Yen
;
Cheng, Yuh-Jen
Patterned sapphire substrates (PSSs) have been used to enhance the performance of GaN-based light-emitting diodes (LEDs). This performance can be further improved by using an ex situ sputtered AlN nucleation layer. This improvement has been attributed to the reduction of the GaN formation on the sidewall of the cone shape pattern. In this study, four kinds of PSS samples were fabricated to investigate the effect of sputtered AlN location on the growth mechanism of GaN in detail. (c) 2017 The Electrochemical Society. All rights reserved.
Electrically driven green, olivine, and amber color nanopyramid light emitting diodes
(2013-10-07)
Chang, Shih-Pang
;
Chang, Jet-Rung
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Sou, Kuok-Pan
;
Liu, Mei-Chun
;
Cheng, Yuh-Jen
We report the fabrication and studies of electrically driven green, olivine, and amber color nanopyramid GaN light emitting diodes (LEDs). InGaN/GaN multiple quantum wells (MQWs) were grown on the nanopyramid semipolar facets. Compared with the commonly used (0001) c-plane MQWs, the semipolar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. This is important for high In content MQWs. The measured internal quantum efficiencies for green, olivine, and amber color LED are 30%, 25%, and 21%, respectively. The radiative and non-radiative lifetime of the semipolar MQWs are also investigated. (C) 2013 Optical Society of America
Enhanced Photoresponse of InN Devices Using Indium-Tin Oxide Nanorods
(2017-01-01)
Hsu, Lung-Hsing
;
Cheng, Yuh-Jen
;
Yu, Peichen
;
Kuo, Hao-Chung
;
Lin, Chien-Chung
Enhanced infrared photoresponse is observed in InN/ITO rods fabricated by LP-MOCVD and oblique-angle electron beam evaporation. The higher growth temperature and more V/III could trend toward hexagonal InN pillars epitaxy. The peak energy blue-shift phenomenon due to higher Fermilevel to acceptor emission was investigated by temperature dependent photoluminescence (PL) measurements. ITO nanorods enhanced the broadband and angle-independent anti-reflection in the range between 400 nm and 2000 nm. The InN/ITO rods photodetection device was demonstrated with enhanced IR response, and the portion photocurrent (610 nm long pass) of InN detection as high as 24.5% measured via AM1.5G solar simulated spectra.
Enhanced Radiative Emission of MQW by Resonant Modes of Hyperbolic Metamaterial Resonator
(2019-01-01)
Shen, Kun-Ching
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Hsu, Lung-Hsing
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Tsai, Din Ping
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Kuo, Hao-Chung
;
Lin, Chien-Chung
We report the use of resonant modes of a hyperbolic metamaterial cube made of multiple metal/dielectric layer structure to enhance the radiative emission of multiple quantum wells. The mode analysis and photoluminescence will be discussed. (C) 2019 The Author(s)
Enhanced Stimulated Emission from Optically Pumped Gallium Nitride Nanopillars
(2011-02-01)
Lo, Ming-Hua
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Cheng, Yuh-Jen
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Kuo, Hao-Chung
;
Wang, Shing-Chung
;
光電工程學系
We report the observation of an enhanced stimulated emission from optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned etching followed by crystalline regrowth. When the sample was optically excited, a strong stimulated emission peak emerged from a broad spontaneous emission background. The emission was attributed to electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping configuration. We remark that the enhancement is due to better gain and photon interaction from the multiple scattering of photons among nanopillars. (C) 2011 The Japan Society of Applied Physics
Fabrication and lasing characteristics of GaN nanopillars
(2011)
Lo, Ming-Hua
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Cheng, Yuh-Jen
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Kuo, Hao-Chung
;
Wang, Shing-Chung
;
光電工程學系
We report the fabrication of GaN nanopillars and their laser action characteristics under optical pumping measurement. The nanopillars were fabricated from a GaN epitaxial wafer by self-assembled Ni nanomasked etching, followed by epitaxial regrowth to form crystalline facets on the etched nanopillars. The regrowth process is intended to reduce surface defects created during ICP-RIE etching. The density of etched GaN nanopillars is about 8.5x10(8)/cm(2) and the diameter and height of GaN nanopillars are about 250 nm and 650 nm, respectively. The as grown GaN nanopillars exhibit a random distribution with hexagonal pillar geometry. The sample is optically excited by frequency tripled Nd:YAG pulsed laser. The Gaussian waist of pumping spot is 1.8 um. At low pumping intensity, the emission has a broad spontaneous emission spectrum with maximum at 363 nm. As pump intensity increases, a narrow peak at 363 nm emerges quickly from the broad spontaneous emission back ground. The lasing action occurs at threshold pump power density of 122 MW/cm(2). The emission linewidth decreases with pumping power across threshold and reaches a lowest value of about 0.38 nm above threshold. The excitation-power-dependent spectra show that the lasing wavelength has a slight blue shift as pump power increases. We remark that this is due the band filling of the increasing excited carrier density.
Growth and Electroluminescent Property of Multi-Facet InGaN/GaN Multiple Quantum Well Light Emitting Device
(2015)
Li, Yun-Jing
;
Chang, Shih-Pang
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Cheng, Yuh-Jen
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Kuo, Hao-Chung
;
Chang, Chun-Yen
We report the study of InGaN/GaN multiple quantum wells (MQWs) grown on multi-facet microrods. The multi-facet MQWs have broad emission spectrum. Electrical injection was demonstrated with emission color ranged from red to blue.
Influence of the microstructure geometry of patterned sapphire substrates on the light extraction efficiency of GaN LEDs
(2016-09)
Kuo, Chien-Ting
;
Hsu, Lung-Hsing
;
Huang, Bo-Hsin
;
Kuo, Hao-Chung
;
Lin, Chien-Chung
The influence of the microstructure geometry of patterned sapphire substrates (PSS) on the light extraction efficiency (LEE) of GaN light-emitting diodes (LEDs) is numerically analyzed. Cone structures of various dimensions are studied, along with dome and mixed microstructures. LEE is found to mainly depend on the microstructure surface slope. LEE rises quickly with slope and flattens out when the slope exceeds 0.6. Scaling down the microstructure has little effect on LEE. Light rays are found to travel longer distances in PSS LEDs, as compared with LEDs grown on a flat substrate. Keeping GaN absorption loss low is important for LEE optimization. (C) 2016 Optical Society of America
InGaN/GaN multiple-quantum-well nanopyramid-on-pillar light-emitting diodes
(2015-04-01)
Li, Yun-Jing
;
Chang, Jet-Rung
;
Chang, Shih-Pang
;
Sou, Kuok-Pan
;
Cheng, Yuh-Jen
We report the study of an electrically driven nanopyramid-on-pillar green light-emitting diode (LED). The pyramid-on-pillar nanostructure was fabricated by top-down etching from a GaN template, followed by epitaxial regrowth. High-In-content InGaN/GaN multiple quantum wells (MQWs) were grown on semipolar pyramid and nonpolar pillar surfaces. The measured radiative lifetimes of MQWs on these two surfaces were 2 orders of magnitude shorter than that of a conventional c-plane (0001) MQW owing to their lower polarization field. Electrical injection performance was also demonstrated and discussed. (C) 2015 The Japan Society of Applied Physics
InN Nanopillar Devices with Strong Photoresponse
(2016-01-01)
Hsu, Lung-Hsing
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Kuo, Chien-Ting
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Cheng, Yuh-Jen
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Chen, Kuan-Chao
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Kuo, Hao-Chung
The InN pillars/p-GaN is promising for extended visible and infrared absorption. The higher growth temperature and more V/III could trend toward hexagonal InN pillars epitaxy, fabricated by a low-pressure metal organic chemical vapor deposition. The tensile strain effect and the peak energy blue-shift phenomenon due to higher Fermi-level to acceptor emission were investigated via Raman and photoluminescence (PL) measurements. The high quality InN pillars reveal no indium droplets by X-ray diffraction pattern. A InN pillars photodetection device is demonstrated with extended IR response, and the portion photocurrent of InN detection as high as 13% measured via AM1.5G solar simulated spectra.
InN Nanopillar Photodetector with Enhanced Infrared Response Using Indium-Tin Oxide Nanorods
(2017-01-01)
Hsu, Lung-Hsing
;
Cheng, Yuh-Jen
;
Yu, Peichen
;
Kuo, Hao-Chung
;
Lin, Chien-Chung
Enhanced infrared photoresponse is observed in InN pillars/ITO rods photodetectors fabricated by LP-MOCVD and oblique-angle electron beam evaporation. The enhanced IR portion photocurrent as high as 19% can be measured via AM1.5G solar simulated spectra.
InN-based heterojunction photodetector with extended infrared response
(2015-11-30)
Hsu, Lung-Hsing
;
Kuo, Chien-Ting
;
Huang, Jhih-Kai
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Hsu, Shun-Chieh
;
Lee, Hsin-Ying
The combination of ZnO, InN, and GaN epitaxial layers is explored to provide long wavelength photodetection capability in the GaN based materials. Growth temperature optimization was performed to obtain the best quality of InN epitaxial layer in the MOCVD system. The temperature dependent photoluminescence (PL) can provide the information about thermal quenching in the InN PL transitions and at least two non-radiative processes can be observed. X-ray diffraction and energy dispersive spectroscopy are applied to confirm the inclusion of indium and the formation of InN layer. The band alignment of such system shows a typical double heterojunction, which is preferred in optoelectronic device operation. The photodetector manufactured by this ZnO/GaN/InN layer can exhibit extended long-wavelength quantum efficiency, as high as 3.55%, and very strong photocurrent response under solar simulator illumination. (C) 2015 Optical Society of America
Lasing action in gallium nitride photonic quasicrystal nanorod arrays
(2012)
Chang, Shih-Pang
;
Sou, Kuok-Pan
;
Chang, Jet-Rung
;
Cheng, Yuh-Jen
;
Li, Yuh-Jing
We report the observation of lasing action from optically pumped gallium nitride nanorod arrays in a quasicrystal pattern. The nanorods were fabricated from a GaN substrate by nanoimprint patterned etching, followed by epitaxial regrowth to form crystalline facets. The imprint was a 12-fold symmetric quasicrystal pattern. The regrowth grew a multiple quantum well core-shell structure on nanorods. The cathodoluminescent emission of quantum wells red shifts from the bottom to top region of nanorod. Under optical pumping, multiple lasing peaks were observed. The lasing modes formed by 12-fold symmetric photonic quasicrystal nanorod arrays are discussed.
Lasing action in gallium nitride quasicrystal nanorod arrays
(2012-05-21)
Chang, Shih-Pang
;
Sou, Kuok-Pan
;
Chen, Chieh-Han
;
Cheng, Yuh-Jen
;
Huang, Ji-Kai
We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed. (C) 2012 Optical Society of America