Browsing by Author "Chen, S. H."

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Conduction control at ferroic domain walls via external stimuli
(2014)
Yang, J. C.
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Yeh, C. H.
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Chen, Y. T.
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Liao, S. C.
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Huang, R.
Intriguing functionalities at nano-sized domain walls have recently spawned a new paradigmfor developing novel nanoelectronics due to versatile characteristics. In this study, we explore a new scenario to modulate the local conduction of ferroic domain walls. Three controlling parameters, i.e., external electrical field, magnetic field and light, are introduced to the 90 degrees domain walls (90 degrees DWs) of BiFeO3. Electrical modulation is realized by electrical transport, where the mobility of 90 degrees DWs can be altered by gating voltage. We further use the ferromagnetic/antiferromagnetic coupling to reveal the inherent magnetism at the DWs. With an established magnetic nature, magneto-transport has been conducted to introduce magnetic controlling parameter, where a giant positive magnetoresistance change can be observed up to 200%. In addition, light modulated conduction, a core factor for multifunctional applications, is successfully demonstrated (current enhancement by a factor of 2 with 11 W white lamp). These results offer new insights to discover the tunability of domain wall nanoelectronics.
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.
Gallium Nitride (GaN) High-Electron-Mobility Transistors with Thick Copper Metallization Featuring a Power Density of 8.2 W/mm for Ka-Band Applications
(2020-02-01)
Lin, Y. C.
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Chen, S. H.
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Lee, P. H.
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Lai, K. H.
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Huang, T. J.
Copper-metallized gallium nitride (GaN) high-electron-mobility transistors (HEMTs) using a Ti/Pt/Ti diffusion barrier layer are fabricated and characterized for Ka-band applications. With a thick copper metallization layer of 6.8 mu m adopted, the device exhibited a high output power density of 8.2 W/mm and a power-added efficiency (PAE) of 26% at 38 GHz. Such superior performance is mainly attributed to the substantial reduction of the source and drain resistance of the device. In addition to improvement in the Radio Frequency (RF) performance, the successful integration of the thick copper metallization in the device technology further reduces the manufacturing cost, making it extremely promising for future fifth-generation mobile communication system applications at millimeter-wave frequencies.
Inactivation of E. coli and B. subtilis by a parallel-plate dielectric barrier discharge jet
(2010-08-15)
Chiang, M. H.
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Wu, J. Y.
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Li, Y. H.
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Wu, J. S.
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Chen, S. H.
Inactivation of Escherichia coli and Bacillus subtilis using the jet region of a parallel-plate air dielectric barrier discharge (DBD) driven by a distorted sinusoidal voltage power supply under atmospheric-pressure condition is reported. Various types of working gases, including pure N(2), pure O(2), and compressed air, were tested. Discharges were characterized electrically by measuring the discharge current, applied voltage and absorbed power, and optically by measuring the optical emission spectra in the UV-visible range and absorption spectra in the IR range. Results of survival rate show that both E. coil and B. subtilis cells (up to 10(7) CFU/mL) can be effectively inactivated using less than 18 passes (1.8 s of residence time in total) of exposure to the post-discharge jet region of compressed air and oxygen discharges at different treating distances in the range of 4-20 mm. Among these, the compressed-air discharge performs the best in inactivating both two types of the bacterial cells, because of the abundant ozone generation and probably through the assistance of nitrous oxide generated in the discharge. In summary, the post-discharge jet region of an oxygen-contained parallel-plate DBD driven by a distorted sinusoidal voltage power driven is very effective in inactivating both E. coli and B. subtilis cells under the present test conditions. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.
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.
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.
SPDT GaAs switches with copper metallized interconnects
(2007-02-01)
Wu, Y. C.
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Chang, E. Y.
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Lin, Y. C.
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Hsu, H. T.
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Chen, S. H.
Copper metallized AlGaAs/InGaAs psedomophic high-electron-mobility transistor (PHEMT) single-pole-double-throw (SPDT) switches utilizing platinum (Pt, 70 nm) as the diffusion barrier is reported for the first time. In comparison with the An metallized switches, the Cu metallized SPDT switches exhibited comparable performance with insertion loss of I Ss than 0.5 dB, isolation larger than 35 dB and the input power for one dB compression (input P-1 dB) of 27 dBm at 2.5 GHz. These switches were annealed at 250 degrees for 20 It for thermal stability test and showed no degradation of the dc characteristics after the annealing. Also, after 144 h of high temperature storage life (HTSL) environment test, these switches still remained excellent and reliable radio frequency (RF) characteristics. It is successfully demonstrated for the first time that the copper metallization using Pt as the diffusion barrier could be applied to the GaAs monolithic microwave integrated circuits switch fabrication with good RF performance and reliability.
Thermodynamic Characterization of Polymorphs in Bulk-Crystallized Syndiotactic Polystyrene via Small/Wide-Angle X-ray Scattering and Differential Scanning Calorimetry
(2009-06-23)
Su, C. H.
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Jeng, U.
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Chen, S. H.
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Cheng, C. -Y.
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Lee, J. -J.
By means of in situ small/wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC), we examined evolutions of lamellar crystal thickness for alpha and beta crystals, respectively, in bulk-crystallized syndiotactic polystyrene (sPS) during the partial melting-reorganization process upon progressive heating up to 290 degrees C. For the SAXS data analysis, the Kratky-Porod approximation proves to be particularly helpful in extracting the crystal thickness when approaching final melting where crystalline lamellae (near equilibration with the melt) exist in low concentrations as dispersed entities instead of in arrays. On the basis of the crystal thicknesses at elevated temperatures under solid-melt equilibration, we constructed melting lines of the two separate forms in the Gibbs-Thomson phase plane. The extrapolated (to infinite lamellar thickness) equilibrium melting temperature T(m,alpha)* approximate to 294 degrees C of the a form is moderately lower than T(m,beta)* approximate to 306 degrees C of the beta form. The two melting lines intercept at a crossover temperature T(Q) approximate to 284 degrees C and crystal thickness l(Q) approximate to 9.6 nm, where the relative thermal stability of the two phases inverses. For crystals thicker than l(Q) (practically hard to reach for bulk crystallization under ambient pressure), the beta form is the stable phase; for crystals thinner than I(Q) (the commonly accessible case), the a form is circumstantially more stable. With crystallinity-corrected values of the heat of fusion Delta H(f,alpha) approximate to 82 MJ m(-3) and Delta H(f,beta) approximate to 146 MJ m(-3) obtained from a combination of DSC and WAXS results, we determined from the slope (= 2 sigma(e)/Delta H(f)) of the melting line that basal surface energy sigma(e,alpha) approximate to 8.2 mJ m(-2) and sigma(e,beta) approximate to 26.8 mJ m(-2) which are considerably lower than those expected for tight folds, indicative of nonadjacently re-entered or loosely looped folds. The combination of lower T(m)*, Delta H(f), Delta S(f), and sigma(e) values renders the a phase highly competitive in the rate of nucleation at low temperatures but much less so at high temperatures as compared to the beta phase. The higher sigma(e,beta) value is also consistent with the observation that the beta phase is more responsive to externally added heterogeneous nucleation agents.