Extended Gate Research Articles

High-performance SEGISFET pH Sensor using the structure of double-gate a-IGZO TFTs with engineered gate oxides

In this paper, we propose a high-performance separative extended gate ion-sensitive field-effect transistor (SEGISFET) that consists of a tin dioxide (SnO2) SEG sensing part and a double-gate structure amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) with tantalum pentoxide/silicon dioxide (Ta2O5/SiO2)-engineered top-gate oxide. To increase sensitivity, we maximized the capacitive coupling ratio by applying high-k dielectric at the top-gate oxide layer. As an engineered top-gate oxide, a stack of 25 nm-thick Ta2O5 and 10 nm-thick SiO2 layers was found to simultaneously satisfy a small equivalent oxide thickness (∼17.14 nm), a low leakage current, and a stable interfacial property. The threshold-voltage instability, which is a fundamental issue in a-IGZO TFTs, was improved by low-temperature post-deposition annealing (∼87 °C) using microwave irradiation. The double-gate structure a-IGZO TFTs with engineered top-gate oxide exhibited high mobility, small subthreshold swing, high drive current, and larger on/off current ratio. The a-IGZO SEGISFETs with a dual-gate sensing mode showed a pH sensitivity of 649.04 mV pH−1, which is far beyond the Nernst limit. The non-ideal behavior of ISFETs, hysteresis, and drift effect also improved. These results show that the double-gate structure a-IGZO TFTs with engineered top-gate oxide can be a good candidate for cheap and disposable SEGISFET sensors.

Extended–gate field effect transistor (EGFET) for carbaryl pesticide detection based on enzyme inhibition assay

An extended – gate filed effect transistor (EGFET) is a device which can be applied to chemical sensing devices. In this study, EGFET was constructed by using an indium tin oxide (ITO) glass substrate. The small piece ITO with sensing area around 3x3 mm2 was used as carbaryl pesticide sensor based on enzyme inhibition assay. The prepared ITO-EGFET sensors were test with pH solutions to obtain sensitivity compared with commercial ion sensitive field effect transistor (ISFET). Preparation of ITO substrate for enzyme inhibition assay by dropped acetylcolinesterase enzyme at 0.5 Unit which were trapped in an agarose gel matrix onto substrates. This prepared ITO acts as extended gate sensing membrane for EGFET. The amounts of drop volume of enzyme were varied to obtain the highest signal for reaction with acetylcholine substrate. Cabaryl can inhibit enzyme function resulting in the decreasing signal of interaction between enzyme and acetylcholine substrate. This ITO-EGFET can be used to detect carbaryl in concentration rage 0.001 – 1 mM by using the ITO-EGFET without enzyme as control condition. This work shows possibility of ITO-EGFET for application in pesticide detection with an easy substrate preparation, low cost and can be applied in field used with others pesticides.

Interdigitated Extended Gate Field Effect Transistor Without Reference Electrode

An interdigitated extended gate field effect transistor (IEGFET) has been proposed as a modified pH sensor structure of an extended gate field effect transistor (EGFET). The reference electrode and the extended gate in the conventional device have been replaced by a single interdigitated extended gate. A metal–semiconductor-metal interdigitated extended gate containing two multi-finger Ni electrodes based on zinc oxide (ZnO) thin film as a pH-sensitive membrane. ZnO thin film was grown on a p-type Si (100) substrate by the sol–gel technique. The fabricated extended gate is connected to a commercial metal-oxide–semiconductor field-effect transistor device in CD4007UB. The experimental data show that this structure has real time and linear pH voltage and current sensitivities in a concentration range between pH 4 and 11. The voltage and current sensitivities are found to be about 22.4 mV/pH and 45 μA/pH, respectively. Reference electrode elimination makes the IEGFET device simple to fabricate, easy to carry out the measurements, needing a small volume of solution to test and suitable for disposable biosensor applications. Furthermore, this uncomplicated structure could be extended to fabricate multiple ions microsensors and lab-on-chip devices.

Ultralow ON-Resistance High-Voltage p-Channel LDMOS With an Accumulation-Effect Extended Gate

The high ON-resistance and the limited breakdown voltage (BV) are the two major issues for the p-channel lateral double-diffused MOSFET (pLDMOS). To solve the two issues, an ultralow specific ON-resistance ( $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}$ ) pLDMOS with improved BV is proposed and investigated by simulation. It features an extended gate (EG) with accumulation effect over the drift region and a P+ floating layer (PFL) in the N-sub. In the ON-state, the EG induces the hole accumulation layer along the drift region surface, providing an ultralow-resistance conducting path. This accumulation-type current transport mode makes $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}$ almost independent of the drift region doping concentration ( $N_{d}$ ) and contributes to a much lower $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}$ , which greatly breaks through the silicon limit of $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}\propto \textrm {BV}^{2.5}$ . In the OFF-state, the EG not only modulates the surface electric field ( $E$ -field) distribution to enhance the BV, but also helps deplete the drift region to increase the optimized $N_{d}$ , and thus further reduce $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}$ . Moreover, the PFL is not depleted, and thus equipotential in the lateral direction. Therefore, the PFL not only modulates the bulk $E$ -field distribution at the source and drain sides but also introduces an additional vertical diode to sustain a higher BV. Owing to the effects mentioned above, the simulated results show that the EG PFL pLDMOS decreases $R_{\mathrm{\scriptscriptstyle ON},\textrm {sp}}$ by 68% and increases the BV by 47% compared with the conventional pLDMOS.

유연한 폴리이미드 기판 위에 구현된 확장형 게이트를 갖는 Silicon-on-Insulator 기반 고성능 이중게이트 이온 감지 전계 효과 트랜지스터

유연한 폴리이미드 기판 위에 구현된 확장형 게이트를 갖는 Silicon-on-Insulator 기반 고성능 이중게이트 이온 감지 전계 효과 트랜지스터

Comparative Sensibility Study of WO3 ph Sensor Using EGFET and Ciclic Voltammetry

In this present study, the investigation about pH sensorial properties of WO3, via sol-gel, was evaluated by Voltammetry and Extended Gate Field Effect Transistor techniques. The X-ray diffractogram indicates the presence of a lamellar structure, d = 0.69 nm, resulting in WO3.2H2O. From Scanning Electron Microscopy of WO3.2H2O was observed a process corresponding to the delamination which consists of irregular stacking with rounded platelets. The WO3.2H2O was investigated as a pH sensor in the pH range 2–12, by the EGFET and Voltametry techniques presenting a sensitivity of 52 mV/pH and 60 mV/pH, respectively. These results can indicate that both Voltammetry and EGFET techniques present values close to the theoretical limit (59.2 mV/pH) as well as the material is a promising candidate for applications as a pH sensor and as disposable biosensor in the future.

High-performance extended gate field-effect-transistor-based dissolved carbon dioxide sensing system with a packaged microreference electrode

We have developed an extended gate field-effect-transistor (EGFET)-based carbon dioxide ( CO 2 ) sensing system with a packaged Ti/Ag/AgCl/KCl-gel microreference electrode using microelectro-mechanical systems (MEMS) technology. The total dimensions of the proposed CO 2 sensing system are only 2.8×1.5×0.1 cm , which is approximately 30 times smaller than a conventional CO 2 sensing system (including the commercial Ag/AgCl RE). All of the manufacturing processes adopted in this work are compatible with standard planar technology and are very suitable for mass production. The presented planar reference electrode shows a very small offset voltage ( −3.0 mV ) and a very small potential drift (2.5 mV in 30,000 s) that is approximately equal to that of the commercial Ag/AgCl RE (1.6 mV in 30,000 s). Additionally, the implemented EGFET-based CO 2 microsensor with a coated CO 2 solid electrolyte and gas permeable membranes on the gate sensing area demonstrates a very high sensitivity ( 44.4 mV/decade ) and very high sensing linearity (98.37%), while sensing CO 2 concentrations ranging from 0.25 to 50 mM. Furthermore, a very small hysteresis voltage (7.5 mV) was obtained during the sensing cycle of 2.5–5–25–50–25–5–2.5 mM; this result was achieved by improving the surface planarization and enlarging the sensing area of the EGFET to 1 mm 2 .

Label-free electrical recognition of a dengue virus protein using the SEGFET simplified measurement system

Separative extended gate field-effect transistor was applied as an immunosensor for the label-free recognition of dengue virus nonstructural protein 1 (NS1).

Indium tin oxide synthesized by a low cost route as SEGFET pH sensor

2 atmosphere using a low-cost chemical vapor deposition (CVD) system. The films were evaluated as pH sensors in separative extended gate field-effect transistor (SEGFET) apparatus, exhibiting a sensitivity of 53 mV/pH, close to the expected Nernstian theoretical value for ion sensitive materials. The use of CVD process to synthesize ITO, as described here, may represent an alternative for fabrication of SEGFET pH sensors at low cost to be used in disposable biosensors since H + ions are the product of several oxireductase enzymes.

A dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor on a silicon-on-insulator substrate

In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor (DGDI LTIGBT) structure, which features a double extended trench gate and a dielectric inserted in the drift region, is proposed and discussed. The device can not only decrease the specific on-resistance Ron,sp, but also simultaneously improve the temperature performance. Simulation results show that the proposed LTIGBT achieves an ultra-low on-state voltage drop of 1.31 V at 700 A·cm−2 with a small half-cell pitch of 10.5 μm, a specific on-resistance Ron,sp of 187 mΩ·mm2, and a high breakdown voltage of 250 V. The on-state voltage drop of the DGDI LTIGBT is 18% less than that of the DI LTIGBT and 30.3% less than that of the conventional LTIGBT. The proposed LTIGBT exhibits a good positive temperature coefficient for safety paralleling to handling larger currents and enhances the short-circuit capability while maintaining a low self-heating effect. Furthermore, it also shows a better tradeoff between the specific on-resistance and the turnoff loss, although it has a longer turnoff delay time.

Glucose Detection Using Fluorine Doped Tin Oxide Extended Gate Field Effect Transistors Upon Varied Functionalizations of Glucose Oxidase

not Available.

High‐breakdown voltage and low on‐resistance AlGaN/GaN on Si MOS‐HEMTs employing an extended TaN gate on HfO 2 gate insulator

Proposed is a new extended gate towards a source in AlGaN/GaN metal-oxide-semiconductor-high-electron-mobility transistors (MOS-HEMTs) in order to increase breakdown voltage and reduce on-resistance. The TaN gate was isolated from the source by a 15 nm-thick RF-sputtered HfO 2 gate insulator. A high breakdown voltage of 1410 V was measured as a result of the successfully blocked gate leakage current and surface passivation by the HfO 2 gate insulator. The extended gate towards the source was an effective method to improve the on-resistance and drain current density by eliminating the gate-source space. The proposed device with the extended gate exhibited low specific on-resistance of 2.28 mΩΩcm 2 while that of the MOS-HEMT with the conventional structure was 2.91 mΩΩcm 2 . Also, maximum drain current density at the V GS of 2 V was increased from 332 to 420 mA/mm by the proposed extended TaN gate.

A Lateral Power MOSFET With the Double Extended Trench Gate

A lateral power MOSFET with the double extended trench gate (DETG) is proposed in this letter. The double extended gate introduces the additional charges into the drift region and the substrate; then, the electric field distribution of the device is optimized to improve the breakdown voltage (BV) and the specific on-resistance (Ron, sp). Simulation results show that the BV of the DETG structure is increased from 126 V of the conventional trench gate (CTG) structure to 171 V with the same length and thickness of the drift region. Furthermore, its Ron, sp is nearly 64% less than that of the CTG structure.

Ion-sensing properties of 1D vanadium pentoxide nanostructures

The application of one-dimensional (1D) V2O5·nH2O nanostructures as pH sensing material was evaluated. 1D V2O5·nH2O nanostructures were obtained by a hydrothermal method with systematic control of morphology forming different nanostructures: nanoribbons, nanowires and nanorods. Deposited onto Au-covered substrates, 1D V2O5·nH2O nanostructures were employed as gate material in pH sensors based on separative extended gate FET as an alternative to provide FET isolation from the chemical environment. 1D V2O5·nH2O nanostructures showed pH sensitivity around the expected theoretical value. Due to high pH sensing properties, flexibility and low cost, further applications of 1D V2O5·nH2O nanostructures comprise enzyme FET-based biosensors using immobilized enzymes.

Dendrimers/TiO2 nanoparticles layer-by-layer films as extended gate FET for pH detection

The layer-by-layer (LbL) technique combined with field-effect transistor (FET) based sensors has enabled the production of pH-sensitive platforms with potential application in biosensors. A variation of the FET architecture, so called separative extended gate FET (SEGFET) devices, are promise as an alternative to conventional ion sensitive FET (ISFET). SEGFET configuration exhibits the advantage of combining the field-effect concept with organic and inorganic materials directly adsorbed on the extended gate, allowing the test of new pH-sensitive materials in a simple and low cost way. In this communication, poly(propylene imine) dendrimer (PPI) and TiO2 nanoparticles (TiO2-np) were assembled onto gold-covered substrates via layer-by-layer technique to produce a low cost SEGFET pH sensor. The sensor presented good pH sensitivity, ca. 57mVpH−1, showing that our strategy has potential advantages to fabricate low cost pH-sensing membranes.

Self-Assembled Films of Dendrimers and Metallophthalocyanines as FET-Based Glucose Biosensors

Separative extended gate field effect transistor (SEGFET) type devices have been used as an ion sensor or biosensor as an alternative to traditional ion sensitive field effect transistors (ISFETs) due to their robustness, ease of fabrication, low cost and possibility of FET isolation from the chemical environment. The layer-by-layer technique allows the combination of different materials with suitable properties for enzyme immobilization on simple platforms such as the extended gate of SEGFET devices enabling the fabrication of biosensors. Here, glucose biosensors based on dendrimers and metallophthalocyanines (MPcs) in the form of layer-by-layer (LbL) films, assembled on indium tin oxide (ITO) as separative extended gate material, has been produced. NH3+ groups in the dendrimer allow electrostatic interactions or covalent bonds with the enzyme (glucose oxidase). Relevant parameters such as optimum pH, buffer concentration and presence of serum bovine albumin (BSA) in the immobilization process were analyzed. The relationship between the output voltage and glucose concentration shows that upon detection of a specific analyte, the sub-products of the enzymatic reaction change the pH locally, affecting the output signal of the FET transducer. In addition, dendritic layers offer a nanoporous environment, which may be permeable to H+ ions, improving the sensibility as modified electrodes for glucose biosensing.

Nanostructured polyaniline thin films as pH sensing membranes in FET-based devices

Polyaniline (PANI) has become an important conducting polymer for sensing due to its morphological and electrical properties. However, the processing of polyaniline in the form of nanostructured thin films is often limited by the low solubility of the polymer in water. We synthesized nanostructured polyaniline (N-PANI) aimed at improving its solubility to form layer-by-layer (LbL) thin films in conjunction with poly(vinyl sulfonic acid) (PVS) as counter ion. N-PANI was characterized via spectroscopic measurements and SEM images. After assembled as LbL thin films onto gold (Au) substrates, the PVS/N-PANI were employed as separative extended gate pH sensing membrane in FET-based devices presenting pH sensitivity around 58 mV/pH with small voltage drift. The results suggest that N-PANI can be easily processed to form suitable thin films for pH sensing and can be combined with biomolecules to be applied in FET-based biosensors.

Modified ion sensitive field effect transistor sensors having an extended gate on a thick dielectric

Modified ion sensitive field effect transistors having an extended gate (EG) on a thick dielectric have been developed to obtain extremely high sensitivity. The capacitance of the EG is controlled to be very small via the thickness of the dielectric layer so that it may be ignored when compared with the gate capacitance of the transistor. As a result, the gate voltage can be fully dependent on the surface charge of the EG. When microalbumin protein of concentration 1 μg/ml on a monoclonal antibody of a microalbumin surface of the EG is injected, an extremely high sensitivity of 1800% is observed.

STUDY ON TIME-CONSTANT MODELS OF SnO2pH SENSOR

The aim of this study was to discuss the hysteresis effect of SnO2 pH sensor based on separative extended gate field effect transistor (SEGFET). Based on the theorem of three time-constants model, hysteresis model is linked with drift effect. Function relationship of pH value and time constant is also derived from the drift effects with difference pH value. Besides, electrochemical impedance spectroscopy (EIS) is utilized to interpret the mechanism of hysteresis effect. Experiments of EIS are carried out in different pH buffer solutions. An equivalent model of sensing membrane is obtained by theorem of EIS. The experimental results indicate that the equivalent circuit elements, such as membrane capacitance and membrane resistance, change with pH. This phenomenon is compared with other literatures and discussed on hysteresis effect.

SODIUM AND POTASSIUM SENSORS BASED ON SEPARATED EXTENDED GATE FIELD EFFECT TRANSISTOR

A double potassium and sodium ions sensor based on separated extended gate field effect transistor (SEGFET) and a new entrapment method are proposed in this study. Having high sensitivity, reproducibility, and a simple manufacturing process, the sensors are quickly able to supply information and detect human blood within an abnormal range. The sensing membranes were fabricated using a Poly(vinyl chloride) carboxylated (PVC-COOH) matrix; sodium ionophore (B12C4) or potassium ionophore (valinomycin). The sensitivity of ion-selective biosensors is 42.55 mV/decade for Na+ between 1 M and 10-7 M, 42.75 mV/decade for K+ between 1 M and 10-6 M.