Browsing by Author "Lin, Chia-Ching"

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A Cu-based alloyed ohmic contact system on n-type GaAs
(2007-12-03)
Chen, Ke-Shian
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Chang, Edward Yi
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Lin, Chia-Ching
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Lee, Cheng-Shih
;
Huang, Wei-Ching
An alloyed Pd/Ge/Cu Ohmic contact to n-type GaAs is reported for the first time. The Pd/Ge/Cu Ohmic contact exhibited a very low specific contact resistance of 5.73x10(-7) Omega cm(2) at a low annealing temperature of 250 degrees C. This result is comparable to the reported Pd/Ge and Au/Ge/Ni Ohmic contact systems to n-type GaAs with doping concentrations about 1x10(18) cm(-3). The Ohmic contact formation mechanisms and microstructure evolution were investigated using secondary ion mass spectrometry, x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometer. The Ohmic contact behavior was related to the formation of Cu(3)Ge and PdGa(x)As(y) compounds after annealing. (c) 2007 American Institute of Physics.
A demonstration of solid-state white light-emitting electrochemical cells using the integrated on-chip plasmonic notch filters
(2016)
Lee, Ya-Ju
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Lin, Chia-Ching
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Lee, Hsiao-Chin
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Yao, Yung-Chi
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Sarma, Monima
In this study, we demonstrate solid-state white light-emitting electrochemical cells (LECs) using an integrated plasmonic notch filter to tailor the electroluminescence (EL) spectrum of non-doped blue-green emissive material. The plasmonic notch filter is composed of randomly distributed silver nanoparticles (Ag-NPs) embedded in the anode contact of indium tin oxide (ITO). This plasmonic notch filter strongly absorbs green light due to local surface plasmon (LSP) resonance of the Ag-NPs embedded in ITO. Thus, the emission green light of the solid-state LEC is strongly suppressed, leaving the blue and red light output to generate a white EL emission. Moreover, the duration of white EL can be maintained for a longer time under operation, which overcomes the issues regarding the short lifetime of white EL generated by the microcavity effect. In addition, the Ag-NPs can be readily fabricated by the thermal annealing of Ag film, which is compatible with current fabrication technologies typically used in light-emitting diode (LED) industry. Therefore, solid-state white LECs using an integrated on-chip plasmonic notch filter have great potential for applications in solid-state lighting.
Application of Pd/Ge/Cu alloyed ohmic contact system to n-type GaAs for fully Cu-metallized InGaP/GaAs HBTs
(2009-02-01)
Chen, Ke-Shian
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Chang, Edward Yi
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Lin, Chia-Ching
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Lee, Cheng-Shih
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材料科學與工程學系
Use of the Pd/Ge/Cu multilayers as the emitter and collector ohmic metal for the fully Cu-metallized InGaP/GaAs heterojunction bipolar transistors is studied. The Pd/Ge/Cu ohmic contact exhibited a very low contact resistance of 5.73 x 10(-7) Omega cm(2) at a low annealing temperature (250 degrees C) and the microstructure evolution of Pd/Ge/Cu ohmic contact was investigated using transmission electron microscopy and energy dispersive spectrometer. We also did some comparisons between the Pd/Ge/Cu, Pd/Ge/Ti/Pt/Cu, and the traditional Au/Ge/Ni/Au ohmic contact structures to n-type GaAs. The common emitter I-V curves and Gummel plot of these Cu-metallized HBTs using Pd/Ge/Cu ohmic contact and Cu interconnects showed similar electrical characteristics as those HBTs with conventional Au-metallization. The cutoff frequency (f(T)) of 3 x 20-mu m-emitter-area devices was about 38 GHz. During both the current-accelerated stress test (110 kA/cm(2) stress for 24 h) and the thermal stability test (annealing at 250 degrees C for 24 h), the fully Cu-metallized HBT with Pd/Ge/Cu ohmic contact and Cu interconnects showed almost no obvious degradation in electrical characteristics. The results show that the Pd/Ge/Cu ohmic contact in combination with the Cu interconnects can be used on HBT devices to achieve the Au-free fully Cu-metallized lnGaP/GaAs HBTs, and the devices exhibit good device performance. (C) 2008 Elsevier Ltd. All rights reserved.
Differential Zero Compensator in Delay-Ripple Reshaped Constant On-Time Control for Buck Converter with Multi-layer Ceramic Capacitors
(2012)
Chen, Wei-Chung
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Lin, Chia-Ching
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Chen, Ke-Horng
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電機工程學系
;
Department of Electrical and Computer Engineering
a differential-zero-compensator (DZC) technology in constant on-time control dc-dc buck converter which can be applied for the ceramic capacitors is proposed in this paper. Ceramic capacitors are widely used in industry because its low cost. However, the stability often confronts with the sub-harmonic problem related to the incorrect output capacitor and ESR used. In this paper, the proposed DZC technology remits the limitation without adding extra pins and the complexity of circuit still maintain simple. Furthermore, the proposed self-compensated on-time timer (ONT) offers the reliable on-time period with linear solution. In addition, utilizing ceramic capacitor derives smaller ripple of 8mV at 8A. High efficiency of 92.5 % can be guaranteed due to the small ESR value. Stability criteria analysis and simulation results demonstrate that the stability can be ensured even if the ESR is small than 2m Omega.
Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons
(2016-03-03)
Yao, Yung-Chi
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Hwang, Jung-Min
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Yang, Zu-Po
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Haung, Jing-Yu
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Lin, Chia-Ching
Enhancement of the external quantum efficiency of a GaN-based vertical-type light emitting diode (VLED) through the coupling of localized surface plasmon (LSP) resonance with the wave-guided mode light is studied. To achieve this experimentally, Ag nanoparticles (NPs), as the LSP resonant source, are drop-casted on the most top layer of waveguide channel, which is composed of hydrothermally synthesized ZnO nanorods capped on the top of GaN-based VLED. Enhanced light-output power and external quantum efficiency are observed, and the amount of enhancement remains steady with the increase of the injected currents. To understand the observations theoretically, the absorption spectra and the electric field distributions of the VLED with and without Ag NPs decorated on ZnO NRs are determined using the finite-difference time-domain (FDTD) method. The results prove that the observation of enhancement of the external quantum efficiency can be attributed to the creation of an extra escape channel for trapped light due to the coupling of the LSP with wave-guided mode light, by which the energy of wave-guided mode light can be transferred to the efficient light scattering center of the LSP.
Enhancing UV-emissions through optical and electronic dual-function tuning of Ag nanoparticles hybridized with n-ZnO nanorods/p-GaN heterojunction light-emitting diodes
(2016)
Yao, Yung-Chi
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Yang, Zu-Po
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Hwang, Jung-Min
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Chuang, Yi-Lun
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Lin, Chia-Ching
ZnO nanorods (NRs) and Ag nanoparticles (NPs) are known to enhance the luminescence of light-emitting diodes (LEDs) through the high directionality of waveguide mode transmission and efficient energy transfer of localized surface plasmon (LSP) resonances, respectively. In this work, we have demonstrated Ag NP-incorporated n-ZnO NRs/p-GaN heterojunctions by facilely hydrothermally growing ZnO NRs on Ag NP-covered GaN, in which the Ag NPs were introduced and randomly distributed on the p-GaN surface to excite the LSP resonances. Compared with the reference LED, the light-output power of the near-band-edge (NBE) emission (ZnO, lambda = 380 nm) of our hybridized structure is increased almost 1.5-2 times and can be further modified in a controlled manner by varying the surface morphology of the surrounding medium of the Ag NPs. The improved light-output power is mainly attributed to the LSP resonance between the NBE emission of ZnO NRs and LSPs in Ag NPs. We also observed different behaviors in the electroluminescence (EL) spectra as the injection current increases for the treatment and reference LEDs. This observation might be attributed to the modification of the energy band diagram for introducing Ag NPs at the interface between n-ZnO NRs and p-GaN. Our results pave the way for developing advanced nano-structured LED devices with high luminescence efficiency in the UV emission regime.
Manipulating magnetoelectric energy landscape in multiferroics
(2020-06-05)
Huang, Yen-Lin
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Nikonov, Dmitri
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Addiego, Christopher
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Chopdekar, Rajesh, V
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Prasad, Bhagwati
Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO3, is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently to exploring the physical properties, especially focusing on ferroelectricity and antiferromagnetism in chemically modified BiFeO3, a concrete understanding of the magnetoelectric coupling is yet to be fulfilled. We have discovered that La substitutions at the Bi-site lead to a progressive increase in the degeneracy of the potential energy landscape of the BiFeO3 system exemplified by a rotation of the polar axis away from the < 111 > (pc) towards the < 112 > (pc) discretion. This is accompanied by corresponding rotation of the antiferromagnetic axis as well, thus maintaining the right-handed vectorial relationship between ferroelectric polarization, antiferromagnetic vector and the Dzyaloshinskii-Moriya vector. As a consequence, La-BiFeO3 films exhibit a magnetoelectric coupling that is distinctly different from the undoped BiFeO3 films. BiFeO3 has a wide application but the impact of rare-earth substitution for the evolution of the coupling mechanism is unknown. Here, the authors reveal the correlation between ferroelectricity, antiferromagnetism, a weak ferromagnetic moment, and their switching pathways in La-substituted BiFeO3.
Reduction of Equivalent Series Inductor Effect in Delay-Ripple Reshaped Constant On-Time Control for Buck Converter with Multi-layer Ceramic Capacitors
(2012)
Chen, Wei-Chung
;
Kang, Yu-Chi
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Lin, Chia-Ching
;
Chen, Ke-Horng
;
Wang, Shih-Ming
The time constant, which is the product of the output capacitor and its equivalent series resistance (ESR), limits the stability of conventional constant on-time control buck converter. To meet the expected requirements, SP-CAP is mostly used as output capacitor although it deteriorates the performance of converter. On the other hand, the multi-layer ceramic capacitors (MLCC) features low cost and small equivalent series resistance (ESR) and is widely used in commercial power management ICs. However, the stability often suffers from the sub-harmonic problem due to small time constant. This paper proposes a differential-zero compensator with the noise margin enhancement (DZC-NME) technique in constant on-time control buck DC-DC converter with ceramic output capacitor. The proposed DZC-NME technique not only eliminates the limit of large time constant but also tolerates the existence of equivalent series inductor (ESL) effect. Simulation result demonstrates the function and shows smaller output ripple of 10mV and high efficiency of 91 % with ESR which smaller than 1m Omega.
Reduction of Equivalent Series Inductor Effect in Delay-Ripple Reshaped Constant On-Time Control for Buck Converter With Multilayer Ceramic Capacitors
(2013-05-01)
Chen, Wei-Chung
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Wang, Ching-Sung
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Su, Yi-Ping
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Lee, Yu-Huei
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Lin, Chia-Ching
The stability of conventional constant on-time control buck converter is constrained by the time constant, which is the product of the output capacitor and its equivalent series resistance (ESR). Specialty polymer capacitor which is mostly used as output capacitor for such a consideration although it limits the performance of converter. On the other hand, the multilayer ceramic capacitors are widely used in commercial power management ICs due to the advantages of low cost and ESR. However, the stability often confronts with the subharmonic problem caused by small time constant. A differential-zero compensator with the noise margin enhancement (DZC-NME) technique in constant on-time control buck dc-dc converter with output ceramic capacitor is proposed in this paper. Thus, the proposed DZC-NME technique not only eliminates the limit of large time constant but also tolerates the existence of equivalent series inductor (ESL) effect. Experiment results demonstrate small output ripple of 10 mV and high efficiency of 91% when ESR is smaller than 1 m Omega and large interference from ESL effect is 40 mV.
Slanted n-ZnO nanorod arrays/p-GaN light-emitting diodes with strong ultraviolet emissions
(2015-02-01)
Yang, Zu-Po
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Xie, Zhong-Han
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Lin, Chia-Ching
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Lee, Ya-Ju
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光電系統研究所
Both of oblique angle deposition and conventional deposition techniques were used by a RF sputtering system to grow the slanted (beta = 32 degrees) and planar (beta = 0 degrees) n-ZnO films on p-GaN, respectively. These two kinds of n-ZnO/p-GaN heterojunctions were then fabricated the light-emitting diodes (LEDs). The electrical and optical properties of these two kinds of LEDs were investigated systematically. The results show that the slanted n-ZnO/p-GaN LEDs have a lower turn-on voltage and less leakage current than that of planar n-ZnO/p-GaN LEDs. Moreover, different from the planar n-ZnO/p-GaN LEDs which emitting colors changes with injection current, the slanted n-ZnO/p-GaN LEDs retains UV emissions (385-400 nm) under the entire range of injection currents we applied. The dominant UV luminescence of slanted n-ZnO/p-GaN LEDs is attributed to the ZnO near band edge transitions, indicating the high quality of slanted ZnO films and exhibiting the essential property dedicated to nano-sized heterojunctions. Hence, we have demonstrated that the slanted n-ZnO/p-GaN LEDs fabricated by oblique angle deposition have better performance than the planar n-ZnO/p-GaN LEDs fabricated by convention deposition means. (C) 2015 Optical Society of America