Browsing by Author "Chang, C. W."

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A band-pass filter consisting of two substrate integrated waveguide cavities coupled by an aperture on their common side wall
(2007-08-01)
Hwang, R. B.
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Chang, C. W.
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電信工程研究所
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Institute of Communications Engineering
In this article, we present a substrate-integrated waveguide-based band-pass filter with wide stop-band rejection property. This band-pass filter is made up of two substrate-integrated waveguide cavities, which couple to each other by all aperture on their common waveguide side wall. By using the empirical formula [19] for obtaining the equivalent rectangular waveguide dimensions, the substrate integrated waveguide structure could then be properly approximated by a closed rectangular waveguide. We employed the rigorous mode-snatching method to analyze the electromagnetic boundary-value problem of the structure containing multiple discontinuities. In comparison with the conventional end-to-end coupled cavity filters, we find that out-new-side-wall-coupled cavity filter can suppress the second resonance frequency and therefore, provide a considerably wide rejection band. It is interesting to note that the suppression of the second resonance frequency can be achieved by properly shifting the second cavity in lateral direction. To explore its physical insight, the resonant modes in the substrate integrated waveguide cavities are carefully inspected. for realizing the physical picture of wave process taking place in the two cavities system. In addition to the theoretical analysis, we have fabricated the filters and measured their scattering parameters. The good agreement between the theoretical and measured results validates the accuracy of numerical computation, and also shows the promising performance of the proposed filters. (c) 2007 Wiley Periodicals, Inc.
Designer germanium quantum dot phototransistor for near infrared optical detection and amplification
(2015-02-06)
Kuo, M. H.
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Lai, W. T.
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Hsu, T. M.
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Chen, Y. C.
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Chang, C. W.
We demonstrated a unique CMOS approach for the production of a high-performance germanium (Ge) quantum dot (QD) metal-oxide-semiconductor phototransistor. In the darkness, low off-state leakage (I-off similar to 0.27 pA mu m(-2)), a high on-off current ratio (I-on/I-off similar to 10(6)), and good switching behaviors (subthreshold swing of 175 mV/dec) were measured on our Ge-QD phototransistor at 300 K, indicating good hetero-interfacial quality of the Ge-on-Si. Illumination makes a significant enhancement in the drain current of Ge QD phototransistors when biased at both the on-and off-states, which is a great benefit from Ge QD-mediated photoconductive and photovoltaic effects. The measured photocurrent-to-dark-current ratio (I-photo/I-dark) and the photoresponsivities from the Ge QD phototransistor are as high as 4.1 x 10(6) and 1.7 AW(-1), respectively, under an incident power of 0.9mW at 850 nm illumination. A superior external quantum efficiency of 240% and a very fast temporal response time of 1.4 ns suggest that our Ge QD MOS phototransistor offers great promise as optical switches and transducers for Si-based optical interconnects.
Development of novel cascade structure for improving stroke of electrostatic comb-drive actuator
(2008)
Chiou, J. C.
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Kuo, C. F.
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Lin, Y. J.
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Chang, C. W.
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Hou, K. C.
In this study, a novel cascade structure for improving the stroke of electrostatic comb-drive actuator is proposed. With the cascade configuration, the stroke can be improving efficiency. The proposed actuators were fabricated through CMOS processes and post-CMOS micromachining steps. Experimental results indicated that the stroke of the lateral and vertical cascade electrostatic comb-drive actuators can be improved 180% and 188% respectively without adding extra driving voltage. These results demonstrated that the proposed cascade configurations have the capability to improve the actuation stroke of electrostatic actuators.
Interruption-free growth of 10 mu m-thick GaN film prepared on sputtered AlN/PSS template by hydride vapor phase epitaxy
(2015-09-15)
Chen, Y. A.
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Kuo, C. H.
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Wu, J. P.
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Chang, C. W.
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照明與能源光電研究所
GaN films (10 mu m-thick) of high crystalline quality were prepared on sputtered AlN/PSS template by hydride vapor phase epitaxy (HVPE). By introducing the two-step growth method into HVPE, one can reduce the steps in the procedure, realize uninterrupted growth, and improve the crystal quality of the films. The effects of initial GaN growth on the AlN/PSS template by HVPE were also investigated. In this study, 10 mu m-thick GaN films prepared on sputtered AlN/PSS template by HVPE showed improved crystal quality using X-ray diffraction and etching pits density. Compared with conventional undoped GaN film grown by metal organic chemical vapor deposition, the full width at half maximum of the (0 0 2) and (1 0 2) peaks of GaN decreased from 450 arcsec to 290 arcsec and from 376 arcsec to 344 arcsec, respectively. Transmission electron microscopy results showed that the gaps observed between the convex regions would eventually turn into dislocations during coalescence, because the number of dislocations increased with the number of gaps observed between the convex regions after step-1 growth. (C) 2015 Elsevier B.V. All rights reserved
Microwave-induced DC currents in mesoscopic structures
(2010-02-01)
Li, L. C.
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Sung, Y. T.
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Chang, C. W.
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Suen, Y. W.
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Chen, K. Y.
We report the power (P) dependence of microwave (MW)-induced current (I(ph)) of a 1-mu m sized mesoscopic structure fabricated from two-dimensional electron gas in the GaAs/AlGaAs heterostructure at temperature of 1.4 K. MW signals were fed onto the sample through a loop antenna nearby and I(ph) is measured from a pair of ohmic contacts. We found that I(ph) is proportional to P at low-P limit; this dependence has been predicted for diffusion-limited electron transport in mesoscopic systems. By contrast, for large P. the dependence is extremely non-monotonous and complicated; even though its physical origin is still not clear so far, our data suggest it is related to the scattering processes from boundaries and impurities in the mesoscopic structure. We also investigated the symmetry properties against reversal of magnetic field (B) and found that the field-symmetric part of I(ph)(B) is consistent with the variation of magnetoresistance; there exists also an anti-symmetric part, which should be related to time-reversal-symmetry-breaking scattering mechanisms in the channel. (C) 2009 Elsevier B.V. All rights reserved.
Surface-Mounted Dry Electrode and Analog-Front-End Systems for Physiological Signal Measurements
(2009)
Chang, C. W.
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Chiou, J. C.
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電控工程研究所
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Institute of Electrical and Control Engineering
In this paper, we present a new analog-front-end system including surface-mounted dry electrode by MEMS dry electrode (MDE) and instrumentation amplifier by chopper-stabilized differential difference amplifier (CHDDA) for physiological signal recording applications. Comparing to traditional electrodes, proposed MDE shows its superior advantages for low electrode skin interface impedance and need not to use electrolytic gel. Moreover, the measured results of the presented CHDDA demonstrated the low power, denoise capability for physiological signal recording. The full AFE system is 4.5(star)7cm(2) in size, weight 35g and can be operated for 200Hr by 2 AAA batteries. Finally, the actual 4 channel AFE recording of EEG, EOG, ECG and EMG proves the practicability of the proposed system.
The Demonstration of Gate Dielectric -fuse 4kb OTP Memory Feasible for Embedded Applications in High -k Metal-gate CMOS Generations and Beyond
(2019-01-01)
Hsieh, E. R.
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Chang, C. W.
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Chuang, C. C.
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Chen, H. W.
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Chung, Steve S.
A 4kb macro of One Time Programming (OTP) memory, implemented by a new breakdown, named dielectric fuse (dFuse) breakdown, has been realized on a foundry pure logic 28nm HKMG CMOS platform. The feature size of a unit cell is 1.5T per cell with 7.5F2. The experimental results show that dFuse macro exhibits high programming (PGM) speed of 100ns at 4V, read time smaller than lOns at 0.75V, and excellent data retention under one -month baking at 150 C. More importantly, the program voltage is weakly dependent on the environmental temperature, suitable for automotive applications. This OTP is also expected to be scalable to advanced node such as FinFET and provides an ideal and reliable solution for the storage purpose in loT and 5G era.
The Impact of the Shallow-Trench Isolation Effect on Flicker Noise of Source Follower MOSFETs in a CMOS Image Sensor
(2018-06-01)
Fan, C. C.
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Chiu, Y. C.
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Liu, C.
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Lai, W. W.
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Cheng, C. H.
The flicker noise of source follower transistors is the dominant noise source in image sensors. This paper reports a systematic study of the shallow trench isolation effect in transistors with different sizes under high temperature conditions that correspond to the quantity of empty defect sites. The effects of shallow trench isolation sidewall defects on flicker noise characteristics are investigated. In addition, the low-frequency noise and subthreshold swing degrade simultaneously in accordance to the device gate width scaling. Both serious subthreshold leakage and considerable noise can be attributed to the high trap density near the STI edge. Consequently, we propose a coincidental relationship between the noise level and the subthreshold characteristic; its trend is identical to the experiments and simulation results.
Uncertainty Assessment of Non-normal Emission Estimates Using Non-Parametric Bootstrap Confidence Intervals
(2016-09)
Tong, L. I.
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Saminathan, R.
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Chang, C. W.
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工業工程與管理學系
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Department of Industrial Engineering and Management
Mitigating global warming problems initially involves reducing greenhouse gas (GHG) emissions, therefore the uncertainty of GHG emission estimates needs to be assessed concisely. Although the uncertainty of GHG emission estimates is generally evaluated using classical confidence interval, quantifying the uncertainty based on non-normal GHG emission estimates or small dataset may lead to a significant bias. Using bootstrap confidence intervals is an effective means of reducing such a bias. This study presents a procedure for constructing four bootstrap confidence intervals to assess the uncertainty of GHG emission estimates for three non-normal distributions (namely, Weibull, Gamma and Beta). These bootstrap confidence intervals are standard bootstrap (SB) confidence interval, percentile bootstrap (PB) confidence interval, Bias-corrected percentiles bootstrap (BCPB) confidence interval and bias-corrected and accelerated (BCa) confidence interval. The sensitivity of bootstrap intervals for emission data is examined under various combinations of sample size and parameters of underlying non-normal distributions using three indices: coverage performance, interval mean, and interval standard deviation. Simulation results indicate that the bootstrap confidence intervals for assessing the uncertainty of emission estimates are highly applicable with small sample size and the data distribution is non-normal. Compared with the classical confidence interval, bootstrap confidence intervals have smaller interval mean and smaller interval standard deviation for small sample size under non-normal distributions. This study recommends BCa confidence interval to assess the uncertainty of the emission estimates as long as sample size is 15 or more and the distribution is non-normal. A case study with emission data of the High-Bleed Pneumatic controllers demonstrates the effectiveness of the proposed procedure