Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa(-1), a fast response time of 15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

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Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring

The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

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Recent Developments in p-Type Oxide Semiconductor Materials and Devices.

The design of analog and RF circuits in CMOS technology has become increasingly more difficult as device modeling faces new challenges in the deep-submicrometer regime and emerging circuit applications. In this paper, we investigate the influence of both channel and gate engineering on the analog and RF performances of double-gate (DG) MOSFETs for system-on-chip applications. The gate engineering technique used here is the dual-metal gate technology, and the channel engineering technique is the conventional halo doping process. For analog applications, importance is given to the subthreshold regime as CMOS circuits operated in this regime are very much attractive for ultralow-power high-gain performances. Gate- and channel-engineered devices show an increase of gain by 45% and 35%, respectively, compared with the single-metal DG MOSFET. The gate-engineered device shows an improvement of 21.6% and 20% in the case of fT and fMAX values, whereas the channel-engineered device exhibits a reduction of fT by 2.7% with nearly equal fMAX.

Influence of Channel and Gate Engineering on the Analog and RF Performance of DG MOSFETs

High-frequency (HF) modeling of MOSFETs for radio-frequency (RF) integrated circuit (IC) design is discussed Modeling of the intrinsic device and the extrinsic components is discussed by accounting for important physical effects at both dc and HF The concepts of equivalent circuits representing both intrinsic and extrinsic components in a MOSFET are analyzed to obtain a physics-based RF model The procedures of the HF model parameter extraction are also developed A subcircuit RF model based on the discussed approaches can be developed with good model accuracy Further, noise modeling is discussed by analyzing the theoretical and experimental results in HF noise modeling Analytical calculation of the noise sources has been discussed to understand the noise characteristics, including induced gate noise The distortion behavior of MOSFET and modeling are also discussed The fact that a MOSFET has much higher "low-frequency limit" is useful for designers and modelers to validate the distortion of a MOSFET model for RF application An RF model could well predict the distortion behavior of MOSFETs if it can accurately describe both dc and ac small-signal characteristics with proper parameter extraction

MOSFET modeling for RF IC design

This paper presents physics-based compact models for the C-V and I-V characteristics of AlGaN/GaN HEMT devices. The contribution of only the first energy level in the triangular quantum well at the AlGaN/GaN interface (where most of the charge carriers of the 2-DEG channel reside) is considered, which resulted in an accurate and simple unified charge control model. Based on this, analytical models of the drain current, the gate charge, and the gate capacitances have been developed. The models cover all the different operating regimes of a device. The excellent agreements between the model and measured C-V and I-V characteristics of devices with different gate lengths have demonstrated the validity of the model.

Compact Charge-Based Physical Models for Current and Capacitances in AlGaN/GaN HEMTs

Preface. MOSFET Device Physics and Operation. MOSFET Fabrication. RF Modeling. Noise Modeling. Proper Modeling for Accurate Distortion Analysis. The BSIM4 MOSFET Model. The EKV Model. Other MOSFET Models. Bipolar Transistors in CMOS Technologies. Modeling of Passive Devices. Effects and Modeling of Process Variation and Device Mismatch. Quality Assurance of MOSFET Models. Index.

Device Modeling for Analog and RF CMOS Circuit Design: Ytterdal/Device

A physically based analytical I-V model that includes self-heating effect (SHE) is presented for fully depleted SOI/MOSFET's. The incorporation of SHE is done self-consistently in a fully closed form, making the model very suitable for use in circuit simulators. The model also accounts for the drain induced conductivity enhancement (DICE) and drain induced barrier lowering (DIBL), channel length modulation (CLM), as well as parasitic series resistances (PSR). Another advantage is the unified form of the model that allows us to describe the subthreshold, the near-threshold and the above-threshold regimes of operation in one continuous expression. A continuous transition of current and conductance from the linear to the saturation regimes is also assured. The model shows good agreement with measured data for a wide range of channel lengths (down to 0.28 /spl mu/m) and film thicknesses (94 nm-162 nm).

Unified physical I-V model including self-heating effect for fully depleted SOI/MOSFET's

As a result of significant advances in submicrometer thin film SOI/MOSFET technology over the last few years, SOI circuit design and simulation are becoming increasingly important in VLSI technology research. Consequently, a need for accurate and efficient SOI device models with a strong physical basis, for use in circuit simulators such as SPICE, has emerged. Up to now, several analytical SOI MOSFET models have been developed. However, these models still need improvements in several areas. Here, we describe a new physics based SOI MOSFET model which emphasizes the use of continual and analytical expressions in all regimes of operation, in order to assure efficiency and good convergence in circuit simulations. To this end, a theory based on the unified charge control model (UCCM) was used for describing the above- and below-threshold regimes with one single expression. Also, continuity in current, output conductance and its derivative are assured at the transition between the linear and the saturation regimes of operation. In addition, the model includes important effects related to short channel and thin film phenomena, to parasitic resistances, and to impact ionization near the drain.

Yuhua Cheng

Papers

Device Modeling for Analog and RF CMOS Circuit Design: Ytterdal/Device

Unified physical I-V model including self-heating effect for fully depleted SOI/MOSFET's

Unified submicrometer soymosfet model for circuit simulation