We demonstrate a high-performance photodetector with multilayer tin diselenide (SnSe2) exfoliated from a high-quality crystal which was synthesized by the temperature gradient growth method. This SnSe2 photodetector exhibits high photoresponsivity of 5.11 × 105 A W-1 and high specific detectivity of 2.79 × 1013 Jones under laser irradiation (λ = 450 nm). We also observed a reproducible and stable time-resolved photoresponse to the incident laser beam from this SnSe2 photodetector, which can be used as a promising material for future optoelectronic applications.
In this paper the strain effects on the performance and reliability of future digital III-V device are discussed. Strain is incorporated in the device during fabrication, packaging, and operation. A high amount of strain can introduce defects and cracks in the epilayer. The band structure of the active device region is also altered due to strain. These strain induced changes determine performance, reliability, and lifetime of the device. Therefore, it is necessary to consider strain effects while designing a device for a particular application. Here, compressive-strain-induced changes are used as design parameters and their impact on the logic performance of the device is studied. It is interpreted that the design significantly decreases the gate leakage current and improves the subthreshold slope.
We investigated the n-type doping effect of hydrazine on the electrical characteristics of a molybdenum disulphide (MoS2)-based field-effect transistor (FET). The threshold voltage of the MoS2 FET shifted towards more negative values (from -20 to -70 V) on treating with 100% hydrazine solution with the channel current increasing from 0.5 to 25 μA at zero gate bias. The inverse subthreshold slope decreased sharply on doping, while the ON/OFF ratio increased by a factor of 100. Gate-channel coupling improved with doping, which facilitates the reduction of channel length between the source and drain electrodes without compromising on the transistor performance, making the MoS2-based FET easily scalable.
In this paper, we have demonstrated a low temperature hydrogen (H2) sensor based on reduced graphene oxide (rGO) and tin oxide nanoflowers (SnO2 NFs) hybrid composite film. The addition of SnO2 NFs into rGO solution inhibits irreversible restacking and agglomeration of rGO and increases the active surface area for interaction with H2. This rGO-SnO2 NFs hybrid film sensor showed an excellent response to H2 at 60 °C at 200 ppm with an improvement of 126% compared to pure rGO which was used as a control sample. The sensor also showed good response and recovery time in comparison to pure rGO film. The highly improved H2 sensing characteristics of rGO-SnO2 NFs hybrid are due to its (a) unique structural geometry that increased the surface area for H2 adsorption, and (b) change in the width of depletion layer at the interface due to H2 interaction.
In the present Letter, we have used magnetocapacitance and magnetoresistance measurements to investigate nonequilibrium phenomena in a bilayer electron system based on GaAs/AlGaAs heterostructures. The magnetic field ramping drives the bilayer electron system out of equilibrium, leading to magnetoresistance hysteresis and spikes. Unlike magnetoresistance, magnetocapacitance results intriguingly show hysteresis even when both layers are in the quantum Hall state. The hysteresis is accompanied by interlayer charge transfer, but the disequilibrium is not limited to interlayer imbalance. Results show that the edge-bulk imbalance can be the initial ground for the appearance of hysteresis. In addition, the nonequilibrium states are observed in which the total, rather than individual, layer densities determine the magnetic field and gate voltage dependencies.
The polarization of fluorescence of molecules in soht ion has been reported to depend upon vaxious f 91 viz. viscosity of the solvent [1]; migration of the excited state energy from the originally excited state molecule to a neighbouring molecule [2]; shape and size of the fluorescent molecule [3]; temperature, hydrogen bonding [4], etc. Perrin's formula giving a correlation between polarization and viscosity is no tab le to explain completely the effect of the solvent on polarization, particulaxly when the viscosity is low. Hydrogen bonding capability of a fluorescent molecule is generally inferred from the alterations in both the activation and the fluorescence wavelengths on changing the solvents. The shifts in activation and fluorescence wavelengths may indicate that the solvent associates with the solute in the ground state, or the excited state, and there is a good possibility that this could be due to hydrogen bonding. But by merely observing the excitation and emission spectra it is not always possible to infer conclusively that hydrogen bonding is taking place [5]. In present investigation it is suggested that fluorescence polarization measurement can be used for detecting hydrogen bonding.
In this work, variations in the channel length and gate oxide thickness are studied for the design optimization of 3300 V 4H-SiC based VDMOSFETs. For this, a batch of 3 wafers was processed and tested for key device characteristics. The results indicate shorter channel length of 0.5 μm leads to an increase in the drain leakage current, thus affecting the breakdown voltage as well. The thinner gate oxide at 50 nm demonstrates better control of threshold voltage with no variations in the gate leakage current distribution as compared to 65 nm.
A review is presented on the advances in InAlAs/InGaAs High Electron Mobility transistors (HEMT) on silicon substrates for high frequency and low noise applications. Although InAlAs/InGaAs HEMTs on InP and GaAs substrates have been much appreciated due to their superior performance, their widespread applications have been hindered due to higher cost of the substrates. Silicon has been used as an alternative substrate considering the benefits of low cost, technological maturity and integration of III-V and silicon technology inspite of the constraints like lattice mismatch and large difference in thermal expansion coefficient.
Alternating current dielectrophoresis (DEP) is an excellent technique to assemble nanoscale materials. For efficient DEP, the optimization of the key parameters like peak-to-peak voltage, applied frequency, and processing time is required for good device. In this work, we have assembled graphene oxide (GO) nanostructures mixed with platinum (Pt) nanoparticles between the micro gap electrodes for a proficient hydrogen gas sensors. The Pt-decorated GO nanostructures were well located between a pair of prepatterned Ti/Au electrodes by controlling the DEP technique with the optimized parameters and subsequently thermally reduced before sensing. The device fabricated using the DEP technique with the optimized parameters showed relatively high sensitivity (∼10%) to 200 ppm hydrogen gas at room temperature. The results indicates that the device could be used in several industry applications, such as gas storage and leak detection.
In this paper, a generalized analysis of Asymmetrically-Recessed Double Gate High Electron Mobility Transistor (DGHEMT) to realize high breakdown voltage is carried out. As with aggressive scaling in FETs the short-channel effects like V th roll-off, degradation in cut-off frequency, transconductance etc becomes unavoidable at nanometer gate-length. Recently, DGHEMT has been proposed by Wichmann et. al. for improved performance and suppression of short-channel effects. Though short-channel effects have been effectively suppressed but the reliability analysis of DGHEMT remains unexplored. In this paper device parameters like potential, electric field profile, drain current have been studied for the improvement in breakdown voltage using Atlas Device simulator.
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