Browsing by Author "Chang, C. Y."

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A Superconducting Magnetization System With Hybrid Superconducting Wire for the Study and Application of Superconductivity
(2012-06-01)
Chen, S. D.
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Yu, Y. T.
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Jan, J. C.
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Lin, F. Y.
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Hwang, C. S.
For the study of high-temperature superconductors and for the application of superconductivity, a superconducting high-field magnetization system with a hybrid superconducting coil was designed. This coil is composed of superconducting wires of three kinds-HTS YBCO 2G-wire, high-field and low-field NbTi wires. Three principal purposes of building this system are to inspect the characteristics of disk-shape bulk YBCO, to develop a HTS-bulk undulator, and to magnetize a portable HTS-bulk high-field magnet for application to a resonant X-ray scattering experiment. With four steps of temperature decrease, a two-stage GM-type cryocooler and liquid nitrogen provide cooling for the magnetization system. The hybrid superconducting coil, two cryogenic systems for the magnetization system and the portable HTS-bulk magnet, and the control and monitor systems that were designed are discussed.
Channel Modification Engineering by Plasma Processing in Tin-Oxide Thin Film Transistor: Experimental Results and First-Principles Calculation
(2017-01-01)
Chiu, Y. C.
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Chen, P. C.
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Chang, S. L.
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Zheng, Z. W.
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Cheng, C. H.
In this paper, we investigated the effects of oxygen plasma treatment on tin oxide (SnOx) thin film transistors (TFTs). By using oxygen plasma treatment on SnOx active channel layer, excess oxygen was incorporated to the channel layer and converted oxygen-deficient SnOx to oxygen-rich SnO2-x, which in turn causes the device operation from p-type to n-type. Tuning the different exposure time of oxygen plasma, the optimal TFT device exhibits n-type properties with an on/off current ratio of 2.6 x 10(4), a very high field-effect mobility of 89 cm(2) V-1 s(-1), and a threshold voltage of -0.95 V. Furthermore, the effects of oxygen plasma treatment on band structure, density of states and electron density difference of the SnOx channel layer were performed by the first-principles calculation using density functional theory. The results show that the oxygen plasma treatment approach has high potential for high-performance TFT applications. (C) 2017 The Electrochemical Society. All rights reserved.
Design of a HTS Magnet for Application to Resonant X-Ray Scattering
(2011-06-01)
Chen, S. D.
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Yu, Y. T.
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Huang, Z. W.
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Jan, J. C.
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Hwang, C. S.
In material research, the characteristics of novel materials vary greatly with the environment. A magnet with a strong field will be developed for an experimental station for resonant X-ray scattering to investigate the magnetic properties of materials. This magnet will be developed with high-temperature superconductor (HTS) bulk YBa(2)Cu(3)O(7) and magnetized with a HTS coil magnet wound with 2G HTS wire. HTS (RE) BCO will be selected to construct the coil of this magnet. Both the bulk and coil magnets will be assembled on the same movable system. The bulk HTS magnet will provide flux density greater than 4 T with a gap 34 mm that can accommodate the sample holder of the experimental station. The bulk magnet will be cooled with cryocoolers to 29 K and the coil magnet to 4.2 K; the coil magnet is separable from the bulk magnet after the field is trapped. We describe the concept of the magnetic-field calculation, the overall design of these magnets, and the cooling algorithm for the bulk HTS magnet system.
Development of rapid and ultrasensitive flexible palladium nano-thin film biosensing electrode for V. Orientalis detection
(2018-12-01)
Wu, C. H.
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Huang, Y. Z.
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Chang, C. Y.
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Chang, C. H.
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生物科技學系
Device linearity comparison of uniformly doped and delta-doped In0.52Al0.48As/In0.6Ga0.4As metamorphic HEMTs (vol 27, pg 535, 2006)
(2006-10-01)
Lin, Y. C.
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Chang, Edward Yi
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Yamaguchi, H.
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Hirayama, Y.
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Chang, X. Y.
Effect of gate sinking on the device performance, of the InGaP/AlGaAs/InGaAs enhancement-mode PHEMT
(2007-02-01)
Chu, L. H.
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Chang, E. Y.
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Chang, L.
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Wu, Y. H.
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Chen, S. H.
An enhancement-mode InGaP/AlGaAs/InGaAs pseudomorphic high-electron mobility transistor using platinum (Pt) as the Schottky contact metal was investigated for the first time. Following the Pt/Ti/Pt/Au gate metal deposition, the devices were thermally annealed at 325 degrees C for gate sinking. After the annealing, the device showed a positive threshold voltage (V-th) shift from 0.17 to 0.41 V and a very low drain leakage current from 1.56 to 0.16 mu A/mm. These improvements are attributed to the Schottky barrier height increase and the decrease of the gate-to-channel distance as Pt sinks into the InGaP Schottky layer during gate-sinking process. The shift in the V-th was very uniform across a 4-in wafer and was reproducible from wafer to wafer. The device also showed excellent RF power performance after the gate-sinking process.
Electrical instability of InGaZnO thin-film transistors with and without titanium sub-oxide layer under light illumination
(2017-03-01)
Chiu, Y. C.
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Zheng, Z. W.
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Cheng, C. H.
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Chen, P. C.
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Yen, S. S.
The electrical instability behaviors of amorphous indium-gallium-zinc oxide thin-film transistors with and without titanium sub-oxide passivation layer were investigated under light illumination in this study. For the unpassivated IGZO TFT device, in contrast with the dark case, a noticeable increase of the sub-threshold swing was observed when under the illumination environment, which can be attributed to the generation of ionized oxygen vacancies within the alpha-IGZO active layer by high energy photons. For the passivated TFT device, the much smaller SS of similar to 70 mV/dec and high device mobility of >100 cm(2)/Vs at a drive voltage of 3 V with negligible degradation under light illumination are achieved due to the passivation effect of n-type titanium sub-oxide semiconductor, which may create potential application for high-performance display.
Growth of very-high-mobility AlGaSb/InAs high-electron-mobility transistor structure on si substrate for high speed electronic applications
(2007-01-08)
Lin, Y. C.
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Yamaguchi, H.
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Chang, E. Y.
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Hsieh, Y. C.
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Ueki, M.
The growth of the AlGaSb/InAs high-electron-mobility transistor (HEMT ) epitaxial structure on the Si substrate is investigated. Buffer layers consisted of UHV/chemical vapor deposited grown Ge/GeSi and molecular beam epitaxy-grown AlGaSb/AlSb/GaAs were used to accommodate the strain induced by the large lattice mismatch between the AlGaSb/InAs HEMT structure and the Si substrate. The crystalline quality of the structure grown was examined by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Finally, very high room-temperature electron mobility of 27 300 cm(2) /V s was achieved. It is demonstrated that a very-high-mobility AlGaSb/InAs HEMT structure on the Si substrate can be achieved with the properly designed buffer layers. (c) 2007 American Institute of Physics.
High efficiency light emitting diode with anisotropically etched GaN-sapphire interface
(2009-07-27)
Lo, M. H.
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Tu, P. M.
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Wang, C. H.
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Hung, C. W.
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Hsu, S. C.
We report the fabrication and study of high efficiency ultraviolet light emitting diodes with inverted micropyramid structures at GaN-sapphire interface. The micropyramid structures were created by anisotropic chemical wet etching. The pyramid structures have significantly enhanced the light output efficiency and at the same time also improved the crystal quality by partially relieving the strain and reducing the dislocation defects in GaN. The electroluminescent output power at normal direction was enhanced by 120% at 20 mA injection current and the output power integrated over all directions was enhanced by 85% compared to a reference sample.
High Mobility InGaZnO Thin Film Transistor Using Narrow-Bandgap Titanium-Oxide Semiconductor as Channel Capping Layer
(2014-01-01)
Hsu, H. H.
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Chiou, P.
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Chiu, Y. C.
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Yen, S. S.
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Chang, C. Y.
High performance IGZO/TiO2 thin film transistors using Y2O3 buffer layers on polycarbonate substrate
(2013-09-01)
Hsu, H. H.
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Chang, C. Y.
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Cheng, C. H.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this work, we fabricate IGZO TFT devices on flexible substrate at room temperature. The IGZO/TiO2 TFT has small subthreshold swing of 0.16 V/dec, but suffers large gate leakage and negative threshold voltage. However, the TiO2 TFT with Y2O3 buffer layers shows improved characteristics including a low threshold voltage of 0.55 V, a small sub-threshold swing of 0.175 V/decade and high field-effect mobility of 43 cm(2)/Vs. Such good performance can be attributed to the enhanced capacitance density and lowered gate leakage owing to the integration of large band gap Y2O3 and low-temperature higher-kappa TiO2.
Highly integrated automotive radar sensor
(2007-08-31)
Cheng, G. F.
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Ho, H.
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Wang, W. T.
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Chang, C. Y.
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Chung, S. J.
The design and measured results of the developed radar sensor for automotive applications are presented. The radar sensor is highly integrated with the transceiver module, antenna and baseband circuits. The proposed antenna is composed of a novel microstrip-line-fed hom antenna and a quasi-optic lens antenna.
Hole transport improvement in InGaN/GaN light-emitting diodes by graded-composition multiple quantum barriers
(2011-10-24)
Wang, C. H.
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Chang, S. P.
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Ku, P. H.
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Li, J. C.
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Lan, Y. P.
Graded-composition multiple quantum barriers (GQB) were designed and incorporated in c-plane InGaN/GaN light-emitting diodes (LEDs) grown on c-plane sapphire substrate to improve hole transport and efficiency droop. The simulation of GQB LED design predicts enhancement of the hole transport in the active region at both low and high current densities. The fabricated LED with GQB structure exhibits lower series resistance and substantially reduced droop behavior of only 6% in comparison with 34% for conventional LED, supporting the improvement of hole transport in our design. (C) 2011 American Institute of Physics. [doi:10.1063/1.3655903]
Investigation of Electrical Characteristics on 25-nm InGaAs Channel FinFET Using InAlAs Back Barrier and Al2O3 Gate Dielectric
(2017-01-01)
Lin, M. H.
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Lin, Y. C.
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Lin, Y. S.
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Sun, W. J.
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Chen, S. H.
We investigated an N-type III-V FinFET with a 25-nm In0.53Ga0.47As channel and a 300-nm In0.52Al0.48As barrier layer on an InP substrate. The In0.52Al0.48As barrier layer is used to suppress leakage current from the InP substrate and the 10-nm Al2O3 film deposited by atomic layer deposition (ALD) can be a robust gate dielectric to mitigate interface traps. The on to off current ratio is approximately three orders of magnitude, the subthreshold swing (SS) is 350 mV/dec, and the maximum driving current density is 130 mu A/mu m at V-G = 1.5 V for InGaAs FinFET with a fin width of 40 nm and gate length of 200 nm. (c) 2017 The Electrochemical Society. All rights reserved.
Morphology and optical properties of zinc oxide thin films grown on Si (100) by metal-organic chemical vapor deposition
(2009-01-01)
Lan, S. M.
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Uen, W. Y.
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Chan, C. E.
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Chang, K. J.
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Hung, S. C.
Undoped zinc oxide (ZnO) thin films were deposited on Si (100) substrates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD). After a nucleation layer of ZnO about 500 A... was deposited, top ZnO films with 320-440 nm in thickness were fabricated at temperatures varying from 450 to 600 A degrees C, respectively. X-ray diffraction analyses demonstrate that all the films grown have polycrystalline wurtzite structure. Scanning electron microscopy observations indicate that ZnO films grow with c-axis aligned grains when the deposition temperature is lower than 600 A degrees C. However, 3D microstructures without c-axis alignment were found when the film was deposited at 600 A degrees C. Room temperature photoluminescence (PL) spectra peaking at 3.27-3.29 eV were observed for the ZnO films grown at 450-600 A degrees C. However, only the spectrum from the film grown at 600 A degrees C could present a high intensity ratio of the ultraviolet band to deep-level emissions, which is above 392 and show a minimum full-width at half-maximum of 99 meV for the ultraviolet band. Temperature-dependent PL measurements from 20 to 300 K exhibited the luminescent mechanism of the present ZnO films to be near band excitonic emission.
Novel chirped multilayer quantum-dot lasers
(2008-01-01)
Lin, G.
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Chang, C. Y.
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Tseng, W. C.
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Lee, C. P.
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Lin, K. F.
Chirped multilayer (N=10) QD lasers with 2-, 3- and 5-layer of longer-, medium-, and shorter-wavelength QD stacks, respectively, were grown in this work. Low threshold current density and high saturated modal gain were achieved in this specially designed QD structure. Empirical gain-current analysis was performed on this chirped multilayer QD structure for the first time. It was consistent with our spectral observations and provided valuable information on carrier recombination in chirped multilayer QD structure. Two novel spectral characteristics were discovered also for the first time. First, simultaneous two-wavelength lasing around threshold was observed under particular gain-loss condition at this specific multilayer structure of QD stacking numbers. Second, at cryogenic temperature, simultaneous two-wavelength lasing emissions switched from longer-wavelength lasing first to shorter-wavelength lasing first with increasing current injection. Non-uniform carrier distribution among chirped multilayer QD structure is evident at low temperature below 200 K from our analysis.
Novel chirped multilayer quantum-dot lasers - art. no. 69970R
(2008)
Lin, G.
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Chang, C. Y.
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Tseng, W. C.
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Lee, C. P.
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Lin, K. F.
Chirped multilayer (N=10) QD lasers with 2-, 3- and 5-layer of longer-, medium-, and shorter-wavelength QD stacks, respectively, were grown in this work. Low threshold current density and high saturated modal gain were achieved in this specially designed QD structure. Empirical gain-current analysis was performed on this chirped multilayer QD structure for the first time. It was consistent with our spectral observations and provided valuable information on carrier recombination in chirped multilayer QD structure. Two novel spectral characteristics were discovered also for the first time. First, simultaneous two-wavelength lasing around threshold was observed under particular gain-loss condition at this specific multilayer structure of QD stacking numbers. Second, at cryogenic temperature, simultaneous two-wavelength lasing emissions switched from longer-wavelength lasing first to shorter-wavelength lasing first with increasing current injection. Non-uniform carrier distribution among chirped multilayer QD structure is evident at low temperature below 200 K from our analysis.
On the Electrical Characteristics of Ferroelectric FinFET Using Hafnium Zirconium Oxide with Optimized Gate Stack
(2018-10-27)
Lin, M. H.
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Fan, C. C.
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Hsu, H. H.
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Liu, C.
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Chen, K. M.
We investigated a short-channel ferroelectric FinFET using a ferroelectric HfZrO thin film as gate dielectrics, and scaled down the channel length to 60 nm to study the short-channel effect and the ferroelectricity. The HfZrO FinFETs exhibited improved short-channel performance including subthreshold swing improvement and reduced drain-induced barrier lowering effect. By using pulsed I-V measurement method, we confirmed that the thickness tradeoff between HfZrO ferroelectric layer and buffered layer are critical to alleviate the influence of interface traps and simultaneously obtain the ferroelectricity in HfZrO FinFET devices with the consideration of sidewall traps. Interface traps may cause unwanted off-state leakage current and mismatching negative capacitance. Here, we demonstrated that the ferroelectric behavior can be achieved by simultaneously increasing HfZrO thickness to obtain the optimized polarization and adopt appropriate buffered layer to screen the traps effect under ferroelectric domain switching. (C) 2018 The Electrochemical Society.
Performance enhancement of GaN-based flip-chip ultraviolet light-emitting diodes with a RPD AlN nucleation layer on patterned sapphire substrate
(2014-08-01)
Lin, B. C.
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Chiu, C. H.
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Lee, C. Y.
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Han, H. V.
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Tu, P. M.
In this work, flip-chip ultraviolet light-emitting diodes (FCUV-LEDs) on patterned sapphire substrate (PSS) at 375 nm were grown by an atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD). A specialized reactive plasma deposited (RPD) AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the FCUV-LEDs with RPD AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the transmission electron microscopy (TEM) image, it can be observed that the tip and incline portion of the pattern was smooth using the RPD AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 7 x 10(7) cm(-2) to 2.5 x 10(7) cm(-2) at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The improvement of light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence measurement and numerical simulation confirm such increase of output power can be attributed to the improvement of material quality and light extraction. (C) 2014 Optical Society of America
Self-assembled In0.22Ga0.78As quantum dots grown on metamorphic GaAs/Ge/SixGe1-x/Si substrate
(2006-09-15)
Hsieh, Y. C.
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Chang, E. Y.
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Luo, G. L.
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Chen, S. H.
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Biswas, Dhrubes
Self-assembled In0.22Ga0.78As quantum dots (QDs) grown on Si substrate with Ge/SiGe as buffer layer grown by metal organic vapor phase epitaxy were investigated. Transmission electron microscopy and atomic force microscopy images were used to observe the size and space distribution of the In0.22Ga0.78As QDs grown on the GaAs/Ge/GeSi/Si layer structure. The influence of the growth temperature on the QDs size and density distribution was investigated. For QDs grown at 450 degrees C, the density of the In0.22Ga0.78As dots was estimated to be 1x10(11) cm(-2) and the In0.22Ga0.78As QDs thickness was 5 ML (monolayer) thick. (c) 2006 American Institute of Physics.