A loadless 4T SRAM powered by gate leakage current with a high tolerance for fluctuations in device parameters

A novel loadless four-transistor static random access memory cell is proposed that consists of two N-type driver MOSFETs and two P-type access ones whose gate leakage currents from word-line are used for holding data in the cell. It is shown that the proposed cell has a higher tolerance for manufacturing device fluctuations compared with the conventional loadless 4T SRAM. Furthermore, it is free from bit-line disturb in contrast to the conventional cell. It is confirmed by simulation in 32nm technology node that the read static noise margin of the proposed cell reaches 138.7% of the six-transistor SRAM cell and that the hold static noise margin can be acceptable when the gate insulator thickness of the P-type access MOSFETs is made thinner than the N-type driver MOSFETs. The retention current for the proposed cell decreases to 66.7% of the 6TSRAM and the data rate in read increases to 125%.

Investigating two−stage degradation of threshold voltage induced by off−state stress in AlGaN/GaN HEMTs

In this work, a two-step degradation phenomenon in D-mode Si3N4/AlGaN/GaN metal-insulator-semiconductor high−electron−transistors (MIS−HEMT) is discussed systematically. During off−state stress, threshold voltage shifts positively for a short duration, and is followed by a negative shift. In contrast, the off−state leakage continues to decrease throughout the entire stress. Results of varied measurement conditions indicate that carrier trapping at different regions dominates this phenomenon. It is interesting that under a large lateral electric field, electron−hole pairs are generated and will then be trapped at the gate dielectric layer. Furthermore, when increasing the stress temperature, impact ionization due to carriers from the gate electrode becomes more severe. Finally, devices with different gate insulator (GI) thicknesses are performed to verify the physical model of the degradation behavior.

Self-oscillating Chemoelectrical Interface of Solution-gated Ion-sensitive Field-effect Transistor Based on Belousov–zhabotinsky Reaction

The Belousov–Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system. However, there are only a few studies on the electrical behavior of pH oscillation induced by the BZ reaction, although numerous studies have been carried out to investigate the mechanisms by which the BZ reaction interacts with redox reactions, which results in potential changes. Needless to say, the electrical characteristic of a self-oscillating polymer gel driven by the BZ reaction has not been clarified. On the other hand, a solution-gated ion-sensitive field-effect transistor (ISFET) has a superior ability to detect ionic charges and includes capacitive membranes on the gate electrode. In this study, we carried out the electrical monitoring of self-oscillation behaviors at the chemoelectrical interface based on the BZ reaction using ISFET sensors, focusing on the pH oscillation and the electrical dynamics of the self-oscillating polymer brush. The pH oscillation induced by the BZ reaction is not only electrically observed using the ISFET sensor, the electrical signals of which results from the interfacial potential between the solution and the gate insulator, but also visualized using a large-scale and high-density ISFET sensor. Moreover, the N-isopropylacrylamide (NIPAAm)-based self-oscillating polymer brush with Ru(bpy)3 as a catalyst clearly shows a periodic electrical response based on the swelling–deswelling behavior caused by the BZ reaction on the gate insulator of the ISFET sensor. Thus, the elucidation of the electrical self-oscillation behaviors induced by the BZ reaction using the ISFET sensor provides a solution to the problems of nonequilibrium chemistry.

USING PERCOLATIVE CRYSTALLINE 0.3 CUO/PVDF NANOCOMPOSITE GATE DIELECTRIC FOR FABRICATING HIGH-EFFECT MOBILITY THIN FILM TRANSISTOR OPERATING AT LOW VOLTAGE

Thin-film transistor (TFT) with various layers of crystalline Poly-vinylidene fluoride (PVDF)/CuO percolative nanocomposites based on Anthracene as a gate dielectric insulator have been fabricated. A device with excellent electrical characteristics at low operating voltages (<1V) has been designed. Different layers (L) of the film were also prepared to achieve the best optimization of ideal gate insulator with various static dielectric constants (εr). Capacitance density, leakage current at 1V gate voltage and electrical characteristics of OFETs with a single and multi layer films have been investigated. This device was showed highest field effect mobility of 2.27 cm2/Vs, a threshold voltage of -1.6V, an exceptionally low sub threshold slope of 380 mV/decade and an on/off ratio of 106. Such a High-ε three layered (3L) PVDF/CuO gate dielectric appears to be highly promising candidates for organic non-volatile memory, sensor and field-effect transistors (FETs).

Performance Enhancement of Pentacene-Based Organic Thin-Film Transistors Using a High-K PVA/Low-K PVP Bilayer as the Gate Insulator

In this study, we proposed using the high-K polyvinyl alcohol (PVA)/low-K poly-4-vinylphenol (PVP) bilayer structure as the gate insulator to improve the performance of a pentacene-based organic thin-film transistor. The dielectric constant of the optimal high-K PVA/low-K PVP bilayer was 5.6, which was higher than that of the single PVP layer. It resulted in an increase in the gate capacitance and an increased drain current. The surface morphology of the bilayer gate dielectric could be suitable for pentacene grain growth because the PVP layer was deposited above the organic PVA surface, thereby replacing the inorganic surface of the ITO gate electrode. The device performances were significantly improved by using the bilayer gate dielectric based upon the high-K characteristics of the PVA layer and the enlargement of the pentacene grain. Notably, the field-effect mobility was increased from 0.16 to 1.12 cm2/(Vs), 7 times higher than that of the control sample.

Chemically Induced pH Perturbations for Analyzing Biological Barriers Using Ion-Sensitive Field-Effect Transistors

Potentiometric pH measurements have long been used for the bioanalysis of biofluids, tissues, and cells. A glass pH electrode and ion-sensitive field-effect transistor (ISFET) can measure the time course of pH changes in a microenvironment as a result of physiological and biological activities. However, the signal interpretation of passive pH sensing is difficult because many biological activities influence the spatiotemporal distribution of pH in the microenvironment. Moreover, time course measurement suffers from stability because of gradual drifts in signaling. To address these issues, an active method of pH sensing was developed for the analysis of the cell barrier in vitro. The microenvironmental pH is temporarily perturbed by introducing a low concentration of weak acid (NH4+) or base (CH3COO−) to cells cultured on the gate insulator of ISFET using a superfusion system. Considering the pH perturbation originates from the semi-permeability of lipid bilayer plasma membranes, induced proton dynamics are used for analyzing the biomembrane barriers against ions and hydrated species following interaction with exogenous reagents. The unique feature of the method is the sensitivity to the formation of transmembrane pores as small as a proton (H+), enabling the analysis of cell–nanomaterial interactions at the molecular level. The new modality of cell analysis using ISFET is expected to be applied to nanomedicine, drug screening, and tissue engineering.