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Nanocontact disorder in InP nanowire devices for the enhancement of visible light and oxygen gas sensitivities
(2017-01-01)
Lin, Yen-Fu
;
Chang, Chia-Hung
;
Hung, Tsu-Chang
;
Liu, Zhaoping
;
Fang, Jiye
InP nanowires, synthesized through a self-seeded growth approach, are used in the fabrication of field-effect transistors which consist of source, drain, and back-gate electrodes. The weak gating voltage dependence implies low carrier concentrations whereas its behavior reveals native n-type doping in InP nanowires. These InP nanowire devices exhibit a vast variation of room-temperature resistance that raises a question about contact resistance. For devices of low room-temperature resistance, electron transport in InP nanowires is investigated using temperature dependent resistance in the temperature range between 80 and 300 K, and it can be analyzed using the model of thermal activation. For other devices of high room-temperature resistance, we take into account nanocontact resistance. Models of both Schottky contact and Mott's variable range hopping (VRH) are considered. The two resistances are connected in parallel to give total contact resistance of InP nanowire devices. After fitting experimental data by the proposed model, we estimate effective Schottky barriers and disorder contributions to nanocontact resistance. The effective Schottky barrier, and the nanocontact Schottky and Mott's VRH resistances are plotted as a function of the device room-temperature resistance which indicates the scale of disorder. Using room-temperature resistance of InP nanowire devices, the devices are classified into nanowire-or contact-dominated devices. The two different class of devices are used to check their photo-and gas-sensitivities. The contact-dominated InP nanowire devices show low dark current and low photocurrent as usual, but these contact-dominated devices give high ratio of photo-to dark-current. That result reveals a high photo-sensitivity for those devices of high nanocontact resistance. On the other hand, for gas sensing experiments, the contact-dominated devices show as well a high ratio of resistance under O-2 to that under N-2 gas exposure. (C) 2017 The Authors. Published by Elsevier B.V.
Nanocontact Disorder in Nanoelectronics for Modulation of Light and Gas Sensitivities
(2015-08-11)
Lin, Yen-Fu
;
Chang, Chia-Hung
;
Hung, Tsu-Chang
;
Jian, Wen-Bin
;
Tsukagoshi, Kazuhito
To fabricate reliable nanoelectronics, whether by top-down or bottom-up processes, it is necessary to study the electrical properties of nanocontacts. The effect of nanocontact disorder on device properties has been discussed but not quantitatively studied. Here, by carefully analyzing the temperature dependence of device electrical characteristics and by inspecting them with a microscope, we investigated the Schottky contact and Mott's variable-range-hopping resistances connected in parallel in the nanocontact. To interpret these parallel resistances, we proposed a model of Ti/TiOx in the interface between the metal electrodes and nanowires. The hopping resistance as well as the nanocontact disorder dominated the total device resistance for high-resistance devices, especially at low temperatures. Furthermore, we introduced nanocontact disorder to modulate the light and gas responsivities of the device; unexpectedly, it multiplied the sensitivities compared with the intrinsic sensitivity of the nanowires. Our results improve the collective understanding of electrical contacts to low-dimensional semiconductor devices and will aid performance optimization in future nanoelectronics.
Broadband Gilbert micromixer with an LO Marchand balun and a TIA output buffer
(2006)
Tseng, Sheng-Che
;
Meng, Chinchun
;
Chang, Chia-Hung
;
Wu, Chih-Kai
;
Hung, Guo-Wei
A single-ended wideband downeonversion Gilbert micromixer is demonstrated in this paper using 0.35-um SiGe BiCMOS technology. Because of the wideband matching property of the micromixer, it can perform broad frequency translation. The TIA is utilized in the IF stage while a broadband Marchand balun is employed not only to generate differential LO signals but also to reserve the wideband operation of the mixer. This singleended wideband mixer has the conversion gain of 15 dB, IP(1dB) of 17 dBm, and IIP(3) of -6.5 dBm and works from 3.5 to 14.5 GHz. The input return loss is below -14 dB and the chip size is 1x1 mm(2).
Dual cross-coupling LNA with forward body bias technique
(2012-08-30)
Chang, Chia-Hung
;
Wang, Tao
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A fully integrated low-power LNA with dual cross-coupling and forward body bias (FBB) techniques is presented. The first cross-coupling circuit is applied at the transconductance stage. By connecting body nodes to each other's source terminals, the body cross-coupling network forms the gate-driven and body-driven simultaneously input stage to gain its effective transconductance, which in turn improves the noise performance and decreases current consumption. In addition, the second capacitor cross-coupling configuration is applied at the input stage to form a feed-forward connection, which results in not only boosting the effective transconductance, but also reducing the influence of the gate noise from the input transistors as well. Moreover, to decrease the overall power consumption further, the FBB technique is employed to lower the supply voltage. The measured noise figure is lower than 3.38 dB and the core circuit consumes only 2.16 mW.
A calibrated direct conversion front-end transmitter with resonant matching techniques for mobile WiMAX/WiBro applications
(2012-05-01)
Chang, Chia-Hung
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A direct conversion front-end transmitter with the properties of high linearity and high single sideband rejection ratio is described in this paper. The transmitter employs two resonant matching techniques to improve its operating bandwidth. The first resonant circuit design is applied at the inter-stage of the LO input buffer in order to achieve a wideband frequency response which ranges from dc to 6 GHz. The second resonant circuit is applied at the power amplifier (PA) driver output stage to increase the matching bandwidth and meet both the Worldwide Inter-operability for Microwave Access (WiMAX) and Wireless Broadband (WiBro) applications simultaneously. In addition, the sideband signal and carrier leakage of this transmitter are further minimized by a proposed calibration circuit design to achieve the error vector magnitude (EVM) specifications. The measured single sideband performance with calibration mechanism demonstrates approximately 15 dB improvement on sideband and carrier suppression. The rejected sideband and carrier signals can be up to 55.19 and 56.31 dBc, respectively. The measured dynamic gain range of the transmitter is 53 dB in 1-dB step with a maximum relative gain error lower than 0.4 dB. The transmitter delivers +0.766 dBm output power with EVM of -34.687 dB for the orthogonal frequency division multiple access (OFDMA) 64QAM-3/4 modulated signals. The measured constellation is minimized to be < 1.5% with output power from -2.3 to -36.2 dBm.
A Direct Conversion Merged LNA-I/Q-Mixer With Noise Reduction Using Dual Cross Coupling for WiMAX/WiBro Applications
(2012-01-01)
Chang, Chia-Hung
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A direct conversion merged low noise amplifier (LNA) and I/Q-mixer with new noise reduction technique is presented in this letter. The merged LNA-I/Q-mixer employs a dual capacitor cross coupling (CCC) technique to improve the circuit noise performance. The first CCC is applied at the transconductance stage of the LNA to increase the effective transconductance, which in turn lowers the noise figure and decreases the current consumption. The second CCC connection is applied at the cascode stage of the LNA, which can reduce the influence of the noise current from cascode transistors. The simulation shows the proposed combination of the LNA and I/Q-mixer configuration with the dual CCC technique can achieve NF 3 dB better than that of conventional merged topologies in a wideband application. The measured NF is lower than 4.55 dB from 2.3 to 2.7 GHz. In addition, low-power and low-cost circuit is realized due to current-reused and inductor-less design at the interface of the LNA and I-Q mixer. The core circuit only consumes 16.83 mW and occupies 0.16 mm(2) area.
A study of grid artifacts formation and elimination in computed radiographic images
(2006-12-01)
Lin, Chih-Yang
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Lee, Wen-Jeng
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Chen, Shyh-Jye
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Tsai, Ching-Hwa
;
Lee, Jei-Han
Computed radiography (CR) has many advantages such as filmless operations, efficiency, and convenience. Furthermore, it is easier to integrate with the picture archiving and communication systems. Another important advantage is that CR images generally have a wider dynamic range than conventional screen film. Unfortunately, grid artifacts and moire pattern artifacts may be present in CR images. These artifacts become a more serious problem when viewing CR images on a computer monitor when a clinic grade monitor is not available. Images produced using a grid with higher frequency or a Potter-Bucky grid (i.e., a moving grid, Bucky for short) can reduce occurrence but cannot guarantee elimination of these artifacts [CR & PACS (2000); Detrick F (2001), pp 7-8]. In this paper, the formation of the artifacts is studied. We show that the grid artifacts occur in a narrow band of frequency in the frequency domain. The frequency can be determined, accurately located, and thus removed from the frequency domain. When comparing the results obtained from the proposed method against the results obtained using previous computer methods, we show that our method can achieve better image quality.
Monolithic broadband Gilbert micromixer with an integrated Marchand balun using standard silicon IC process
(2006-12-01)
Tseng, Sheng-Che
;
Meng, Chinchun
;
Chang, Chia-Hung
;
Wu, Chih-Kai
;
Huang, Guo-Wei
A single-ended wideband downconversion Gilbert micromixer is demonstrated in this paper using 0.35-mu m SiGe BiCMOS technology. A transimpedance amplifier with resistive feedback is utilized in the IF stage while a broadband Marchand balun is employed to generate wideband differential local oscillator signals. The planar Marchand balun topology employed in this paper can generate truly balanced signals even in the presence of the lossy low-resistivity (similar to 10 Omega (.) cm) silicon substrate. A systematic approach to measure the frequency response of each individual stage in a Gilbert mixer is developed in this paper. This single-ended wideband mixer has the conversion gain of 15 dB, IP1dB of -19 dBm, IIP3 of -7 dBm, and the noise figure of 13 dB. The mixer works from 3.5 to 14.5 GHz.
Robust model matching design methodology for a stochastic synthetic gene network
(2011-03-01)
Chen, Bor-Sen
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Chang, Chia-Hung
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Wang, Yu-Chao
;
Wu, Chih-Hung
;
Lee, Hsiao-Ching
Synthetic biology has shown its potential and promising applications in the last decade. However, many synthetic gene networks cannot work properly and maintain their desired behaviors due to intrinsic parameter variations and extrinsic disturbances. In this study, the intrinsic parameter uncertainties and external disturbances are modeled in a non-linear stochastic gene network to mimic the real environment in the host cell. Then a non-linear stochastic robust matching design methodology is introduced to withstand the intrinsic parameter fluctuations and to attenuate the extrinsic disturbances in order to achieve a desired reference matching purpose. To avoid solving the Hamilton-Jacobi inequality (HJI) in the non-linear stochastic robust matching design, global linearization technique is used to simplify the design procedure by solving a set of linear matrix inequalities (LMIs). As a result, the proposed matching design methodology of the robust synthetic gene network can be efficiently designed with the help of LMI toolbox in Matlab. Finally, two in silico design examples of the robust synthetic gene network are given to illustrate the design procedure and to confirm the robust model matching performance to achieve the desired behavior in spite of stochastic parameter fluctuations and environmental disturbances in the host cell. (C) 2010 Elsevier Inc. All rights reserved.
A silicon monolithic phase-inverter rat-race coupler using spiral coplanar striplines and its application in a broadband Gilbert mixer
(2008-08-01)
Tseng, Sheng-Che
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Meng, Chinchun
;
Chang, Chia-Hung
;
Chang, Shih-Hsien
;
Huang, Guo-Wei
This paper realized a broadband uniplanar phase-inverter rat-race coupler using a standard silicon process, and then analyzed this coupler under a lossy condition. A phase inverter is employed in this coupler, not only to extend the operation bandwidth, but also to generate balanced outputs by providing equal lossy paths, while symmetrical spiral-shaped coplanar striplines (CPSs) are also utilized to shrink the coupler size, as well as to construct a phase inverter in the middle of one of spiral CPSs. The lossy CPS, when designed as a distortionless line, has a real characteristic impedance, and thus, perfect port matching of the coupler can be achieved at the center frequency. The operation frequency of this silicon monolithic rat-race coupler with the size of 0.5 mm(2) is extremely wide and ranges from 5 to 23 GHz. The dissipated loss, transmission coefficient, and isolation of the rat-race coupler are approximately 5.5, -8, and below -25 dB, respectively. In addition, a wideband Gilbert micromixer with an integrated uniplanar phase-inverter rat-race coupler at the local oscillator port is demonstrated using 0.35-mu m SiGe BiCMOS technology. This mixer works from 2.5 to 13 GHz with 12-dB conversion gain, -16-dBm IP(1) (dB), -4-dBm IIP(3), and 14-dB noise figure. The chip size of the mixer with an integrated coupler is approximately 1.4 mm x 1.4 mm.

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