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Quenching effect of photoconductive semiconductor material has important applications in areas like detecting semiconductor defect and infrared light. In this paper, vapor–liquid–solid (VLS) method is improved to grow nanowires by using a heat resisting quartz tube as the vessel. With the conditions of gold catalysis, appropriate temperature, and ease of handling, gradient-bandgap CdSSe nanowires were grown successfully. We study the quenching effect of different component parts of the nanowire, respectively, and find that the quenching degree increases with the increasing optical intensities of different bandgap nanowires when the power injection is below 10 − 8 W. However, since more recombination centers would turn into the trap energy level centers leading to more electrons to jump into the conduction band with the increasing density of CdS, the peak of quenched rate for 90% CdS proportion nanowire arrives earlier than 90% CdSe proportion, and the peak of quenched rate for CdSe still does not appear even when the optical intensity reaches 10 − 6 W. Our experiment provides an effective and convenient method for the defect-level detection of semiconductor materials, and can also develop high resolution infrared detectors under the material limitation conditions. [ABSTRACT FROM AUTHOR]

A low-voltage low-power Sigma-Delta modulator for health monitoring system is designed using a standard 0.18m CMOS technology. To achieve high accuracy with low power consumption in low supply voltage environment, the designed modulator is implemented with a one-bit third-order topology, in which the input-feedforward structure and switched-opamp (SO) technique are combined. Using the proposed design method, the SO meets the system requirements with the minimal power consumption and good stability in a feedback loop. The modulator achieves 86dB dynamic range (DR) over a 300Hz bandwidth with an oversampling ratio (OSR) of 128, while it occupies 0.16mm2 and consumes 12W under a 1.1V supply. [ABSTRACT FROM AUTHOR]

High frequency (HF) AC and noise modeling of MOSFETs for radio frequency (RF) integrated circuit (IC) design is discussed. Equivalent circuits representing both intrinsic and extrinsic components in a MOSFET are analyzed to obtain a physics-based RF model. Modeling of the intrinsic device and the extrinsic components is discussed by accounting for the important physical effects at both DC and HF. Based m the Y-parameter analysis of the equivalent circuit model, procedures of the HF model parameter extraction are also developed. With the discussed approaches, a sub-circuit RF model incorporating the modeling of parasitics is presented. This model is compared with the measured data for both y parameter and f[sub T] characteristics. Good model accuracy is achieved against the measurements for a 0.25µm RF CMOS technology. The non-quasi-static (NQS) modeling issue has also been discussed by using the BS1M3v3 based RF model to predict the HF characteristics of devices with serious NQS effects. Further, noise modeling issues are discussed by analyzing the theoretical and experimental results in both the flicker noise and thermal noise modeling. Modeling efforts to incorporate new physical effects are needed to predict better the flicker noise characteristics in today's MOSFETs. A detailed analysis of the HF noise parameters has been conducted to establish the relationship between the noise parameters preferred by circuit designers and obtained by HF noise measurement. Analytical calculation of the noise parameters has also been discussed to understand the noise characteristics with/without some parasitic components such as gate and substrate resistances as well as the influence of the induced gate noise. The HF noise predictivities of several HF noise models are also examined with the measured data. The results show that the BSIM3v3 based RF model can predict the channel thermal noise better than the other models. [ABSTRACT FROM AUTHOR]