Electrical property comparison and charge transmission in p-type double gate and single gate junctionless accumulation transistor fabricated by AFM nanolithography

ABSTRACT: The Junctionless nanowire transistor is promising alternative for a new generation of nanotransistors. In this letter the Atomic force microscopy (AFM) nanolithography with two wet etching processes implemented to fabricate simple structures as Double gate and Single gate Junctionless silicon nanowire transistor on low doped p-type Silicon on insulator (SOI) wafer. Etching process was developed and optimized in the present work compared to our previous works.The output and transfer characteristics, and drain conductance of both structures were compared. The trend for both devices found to be the same but the differences in subthreshold swing, On/Off ratio and threshold voltage were observed. The devices are On state performing as the pinch-off devices. The positive gate voltage shows pinch-off effect while the negative gate voltage unable to make a significant effect on drain current. The charge transmission in devices is also investigated in simple model according to Junctionless transistor principal.     

Gate leakage current induced trapping in AlGaN/GaN Schottky-gate HFETs and MISHFETs

This study examined the correlation between the off-state leakage current and dynamic on-resistance (R_ON) transients in AlGaN/GaN heterostructure field-effect transistors (HFETs) with and without a gate insulator under various stress conditions. The R_ON transients in a Schottky-gate HFET (SGHFET) and metal-insulator-semiconductor HFET (MISHFET) were observed after applying various amounts of drain-source bias stress. The gate insulator in the MISHFET effectively reduced the electron injection from the gate, thereby mitigating the degradation in dynamic switching performance. However, at relaxation times exceeding 10 ms, additional detrapping occurred in both the SGHFET and MISHFET when the applied stress exceeded a critical voltage level, 50 V for the SGHFET and 60 V for MISHFET, resulting in resistive leakage current build-up and the formation of hot carriers. These high-energy carriers acted as ionized traps in the channel or buffer layers, which subsequently caused additional trapping and detrapping to occur in both HFETs during the dynamic switching test conducted.     

DC and RF performance of surface channel MESFETs on H-terminated polycrystalline diamond

DC and RF performance of submicron gate-length metal–semiconductor field effect transistors (MESFETs) fabricated on hydrogen-terminated polycrystalline diamond is investigated in detail for different material electronic quality (grain size in the range 100–200 µm) and device geometry (drain-source channel length in the range 1–3 µm). DC characteristics appear almost independent of both properties, giving maximum drain-source current values in the range 120–140 mA/mm in MESFETs having same gate length (0.2 µm) and gate width (25 µm). The layer properties underneath the hydrogenated surface seem then to affect the DC behaviour to a lesser extent when the same hydrogenation procedure is used. At variance, the electronic quality of diamond layers employed for MESFETs realization largely affects the RF performance, resulting into a low oscillation frequency f_max for a MESFET realized by a self-aligned process (1 µm drain-source channel length) onto low quality diamond polycrystalline film. Such a performance improves to f_max = 35 GHz for devices realized onto large grain polycrystalline diamond, although fabricated without self-aligned gate procedure (3 µm drain-source channel length). These findings are discussed in terms of different roles played by surface hydrogenation, device geometry detail and electronic quality of the polycrystalline diamond substrate for MESFET realization.     

Low-voltage SnO₂ nanowire transistors gated by solution-processed chitosan-based proton conductors

Recently, a bioprotonic field-effect transistor with chitosan nanowire channel was demonstrated [Nat. Commun., 2011, 2, 476]. Here, it is interesting to find that solution-processed chitosan films with a large electric-double-layer (EDL) specific capacitance can also be used as the gate dielectrics for low-voltage individual SnO(2) nanowire transistors. The field-effect electron mobility, current on/off ratio and sub-threshold slope of such a hybrid SnO(2) nanowire device is estimated to be 128 cm(2) V(-1) s(-1), 2.3 × 10(4) and 90 mV per decade, respectively. Such low-voltage nanowire EDL transistors gated by chitosan-based proton conductors are promising for nanosensors and bioelectronics.     

Numerical analysis of the electrical failure of a metallic nanowire mesh due to Joule heating

To precisely examine the electrical failure behavior of a metallic nanowire mesh induced by Joule heating (i.e., melting), a previously developed numerical method was modified with regard to the maximum temperature in the mesh and the electrical resistivity of the nanowire. A sample case of an Ag nanowire mesh under specific working conditions was analyzed with highly accurate numerical results. By monitoring the temperature in the mesh, the current required to trigger the melting of a mesh segment (i.e., the melting current) could be obtained. The melting process of a mesh equipped with a current source during actual operation was predicted on the basis of the obtained relationship between the melting current and the corresponding melting voltage in the numerical melting process. Local unstable and stable melting could be precisely identified for both the current-controlled and voltage-controlled current sources in the present example.     

Sensing properties of different classes of gases based on the nanowire-electrode junction barrier modulation

The role of contact between semiconducting nanowire and metal electrodes in a single nanowire field effect transistor (NW-FET) is investigated for the sensing of different type of gases. Two different types of In(2)O(3) nanowire devices, namely; Schottky contact device (SCD) and Ohmic contact device (OCD) are evaluated. SCD has shown a superior response to the reducing gas (CO) compared to oxidizing gas (NO), while OCD has shown high sensitivity towards oxidizing gas (NO) compared to the reducing gas (CO) under similar working conditions. The sensing mechanism is dominated by the contact resistance at the metal-semiconductor junction in SCD and the change in nanowire channel conductance dominates in OCD. The Schottky barrier height (SBH) was extracted using low temperature current voltage measurement which provided direct evidence for the notion that the barrier height plays a crucial role in the sensing of different types of gases. The sensing mechanism is illustrated in this work for both devices.     

水热法一步合成β—MnO2纳米线束

以商业γ—MnO2粉末作为反应前驱物,水热法一步合成了由β-MnO2组装而成的纳米线束。所制备的样品用X射线粉末衍射（XRD）、透射电子显微镜（TEM）、电子衍射（ED）、场发射扫描电子显微镜（FESEM）等测试手段进行了表征。结果表明,所制备样品为纯相四方晶型的单晶β-MnO2纳米线束,直径约20—30nm,长达数微米到数十微米。对β-MnO2纳米线束的形成机理进行了探讨,认为由商业γ—MnO2粉末水热合成β-MnO2纳米线束的过程,是一典型的固体-溶液-固体转变过程,其中包含了Ostwald熟化过程。     

ZnO photoanodes with different morphologies grown by electrochemical deposition and their dye-sensitized solar cell properties

In this article, we grew zinc oxide (ZnO) samples with different morphologies, e.g. film, nanowire and nanosheet, with electrochemical deposition (ECD) by controlling the precursor concentration and the growth mechanism was also discussed. The morphology influence on the photovoltaic conversion efficiency of the dye-sensitized solar cells (DSSC) assembled with different ZnO photoanodes was investigated by measuring current density–voltage (J–V) curve, quantum efficiency (QE) spectrum and electrochemical impedance spectrum (EIS). It was found that the DSSC constructed with ZnO nanowire array as photoanode can absorb more dye, improve the photon utilization rate and provide rapid collection channels for the photoexcited carriers. Therefore, the photovoltaic conversion efficiency of ZnO nanowire DSSC was improved.     

Fabrication of diamond in-plane-gated field effect transistors using oxygen plasma etching

Diamond dual in-plane-gated field effect transistors with very low gate leakage current have been fabricated on an undoped hydrogen-terminated diamond p-type surface using oxygen plasma etching. Adjusting the threshold voltage optimally by one side gate, lateral electric field from the other side gate modulates the channel conductance. The oxygen plasma etching of 60 nm in depth fully isolated the channel of the hydrogen-terminated diamond surface conductive layer from the side gates resulting very low gate leakage current (<1 pA at −60 V) at room temperature. This feature provides a necessary condition for the fabrication of diamond single-hole transistors operated at room temperature.     

Performance Enhancement of GAA Multi-Gate Nanowire with Asymmetric Hetero-Dielectric Oxide

Silicon - In this paper, a Multi-gate asymmetric hetero-dielectric oxide gate all around nanowire MOSFET device (MG-AHD–GAA-NW) is proposed for the low power standby, memory and sensor...     

Memory effects of carbon nanotube-based field effect transistors

In this paper, we report the study on the non-volatile memory effects of carbon nanotube-based field effect transistors (CNTFETs), in which semiconducting single-wall carbon nanotubes (SWNTs) bridge the gold electrodes and the doped silicon substrate acts as the back gate. We find that our CNTFETs exhibit good performance with on/off ratio of more than 10⁴ and they also show strong memory effects. Hysteretic behaviors of the drain current as a function of the gate voltage are clearly observed at room temperature. The threshold voltage shift increases with increasing the sweeping range of the gate voltage. The CNTFET memory effects show good charge retention capability with the data storage time of around 7 days at ambient condition. Besides, the threshold voltage shift of the as-prepared CNTFETs is found to decrease with time and saturate after around 3 days. Water and alcohol molecules adsorbed on the carbon nanotube are suggested to be the origin of the phenomena. It is also observed that the threshold voltage shift in “top-contact” structures is larger than those in “bottom-contact” structures at the same gate voltage sweeping range.     

Temperature-dependent electrical transport properties in graphene/Pb(Zr0.4Ti0.6)O3 field effect transistors

We report the temperature and gate voltage dependent electrical properties of PZT gated graphene field effect transistors (PZT-GFETs) in the vacuum atmosphere. The PZT-GFETs exhibit p-type characteristics which are attributed to the chemical doping induced the Fermi level shifting below the Dirac point. Meanwhile, it also shows a large memory window. The temperature dependencies of the source-drain current in the range of 20–300 K indicate thermally activated hysteresis behaviors. The hysteresis in the transfer characteristics of PZT-GFETs shows a simultaneous enlargement with increasing temperature. The hysteresis appears to stem from the screening of charges that are transferred from graphene to traps at the interface of PZT and graphene. The magnitude of the charge neutrality point under opposite gate voltage sweep are enhanced with the increase of temperature and gate voltage can be ascribed to the common effects of the temperature and voltage magnitude dependent mechanisms such as interface charge trapping process and the polarization effects of PZT films.     

Solution-processed germanium nanowire-positioned Schottky solar cells

Germanium nanowire (GeNW)-positioned Schottky solar cell was fabricated by a solution process. A GeNW-containing solution was spread out onto asymmetric metal electrodes to produce a rectifying current flow. Under one-sun illumination, the GeNW-positioned Schottky solar cell yields an open-circuit voltage of 177 mV and a short-circuit current of 19.2 nA. Schottky and ohmic contacts between a single GeNW and different metal electrodes were systematically investigated. This solution process may provide a route to the cost-effective nanostructure solar architecture.     

Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes

The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode.     

A pH sensor based on electric properties of nanotubes on a glass substrate

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of an n-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that the p-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface.     

Carbon nanotubes field emission devices grown by thermal CVD with palladium as catalysts

The effects of palladium (Pd) catalyst film thickness and ammonia (NH₃) in thermal chemical vapor deposition (CVD) growth of carbon nanotubes (CNTs) are systematically compared per the resulting morphologies, Raman spectra and field emission characteristics. The CNT field emitters were tested under identical experimental configurations. Field emission characteristics were described with Fowler-Nordheim field emission theory. Experimental results demonstrate that thermally grown CVD CNTs configured as diode field emitters exhibit low turn-on fields and high emission current density. The work is extended to include the study of gated field emitters or field emission triode, important to achieving high-resolution, full gray-scale imaging for field emission, flat-panel displays. The gated device was fabricated utilizing single-mask, self-aligned gate electrode with conventional integrated-circuit (IC) fabrication process. The CNT-triode showed gate-controlled modulation of emission current where higher gate voltage gives rise to higher anode currents. The triode fabrication process using silicon-on-insulator (SOI) wafers is discussed.     

An Intensive Study on Assorted Substrates Suitable for High JFOM AlGaN/GaN HEMT

Silicon - The performance comparison and the temperature profile of AlGaN/GaN HEMT on different substrates are investigated. It results the maximum drain-source current (IDS) of 1.08 A/mm, 1.04...     

Tunneling Current-Voltage Controls,Oscillations, and Instability of Nanotube- and Nanowire-Based Nanoelectromechanical Systems

In this paper, vibrations, instability, and control of nanotube- and nanowire-based nanoelectromechanical systems (NEMS) are investigated. A dynamic analysis is presented, which includes the role of the electric field, van der Waals forces, temperature, and the uncertainty principle. Furthermore, the system instability, arising at the so-called pull-in voltage and corresponding to the on-off transition of the device, is also quantified. Active current and voltage controls based on the quantum tunneling effect are discussed. It is shown that the tunneling current between the cantilever nanotube/nanowire tip and the electrode substrate would correspond to the realization of an analogic device (e.g., nanotweezers) if the current is in control or to a digital device (e.g., nanoswitch) if the voltage is controlled. Finally, the characteristic electromechanical curves voltage/current-displacement for the NEMS are deduced.Original English Text Copyright © 2005 by Fizika i Khimiya Stekla, Pugno.This article was submitted by the author in English.     

Combining diamond electrodes with GaN heterostructures for harsh environment ISFETs

Electrochemistry and biochemistry have always been ideal applications for diamond due to its chemical inertness and stability, sensitivity and biocompatibility. Several diamond ChemFET concepts have been proposed to date, however further improvements are still needed to obtain functional devices that can be operated efficiently beyond the reach of the well established silicon ISFET technology [P. Bergveld, Sensor and Actuators B, Chem. 88 (2003), pp. 1].In this paper we describe a novel ISFET structure in which a boron doped diamond electrochemical gate electrode is combined and monolithically integrated with an InAlN/GaN HEMT structure. The new device merges the high chemical stability of diamond with the high transconductance and low pinch-off voltage of InAlN/GaN heterostructure FETs, resulting in a highly stable ISFET with high sensitivity. First devices have been fabricated and electrochemically characterized, expressing high current levels, a pH sensitivity of about 50 mV/pH, complete current modulation when operated within the electrochemical window of the electrode in the range of pH 1 to pH 13 and high stability upon pH cycling and the application of high anodic overpotentials.     

Design and Analysis of Gate Overlapped/Underlapped NWFET Based Lable Free Biosensor

Silicon - In this paper, gate all around (GAA) nanowire P-channel FET label free biosensor is proposed with cavity. Proposed structure is label free so it doesn’t require selective material...