Electrical characteristics and optoelectronic properties of metal-semiconductor-metal structure with zinc oxide nanowires across Au electrodes

This paper reports on a method of assembling semiconducting ZnO nanowires onto a pair of Au electrodes to construct a metal--semiconductor metal （MSM） structure by dieleetrophoresis and studying on its electrical characteristics by using current-voltage （Ⅰ - Ⅴ） measurements. An electronic model with two back to back Sehottky diodes in series with a semiconductor of nanowires was established to study the electrical transport of the MSM structures. By fitting the measured Ⅰ - Ⅴ characteristics using the proposed model, the parameters of the Schottky contacts and the resistance of nanowires could be acquired. The photoelectric properties of the MSM structures were also investigated by analysing the measurements of the electrical transports under various light intensities. The deduced results demonstrate that ZnO nanowires and their Schottky contacts with Au electrodes both contribute to photosensitivity and the MSM structures with ZnO nanowires are potentially applicable for photonic devices.

GaN-based MSM photovoltaic ultraviolet detector structure modeling and its simulation

Based on the principles of metal-semiconductor-metal Schottky barrier photodetectors（MSM-PD）, using the carrier rate equations,the circuit simulation model of a GaN-based MSM photovoltaic ultraviolet detector is constructed through an appropriately equivalent process.By using the Pspice analytical function of Cadence soft on the model,the relationship between the photocurrent and the terminal voltage under different UV light powers is analyzed.The result shows that under the given UV power,the photocurrent increases and tends to become saturated gradually as the terminal voltage of the device increases,and that under different UV powers,the photocurrent increases with increasing incident power.Then the analysis of the relationship between the photocurrent and the terminal voltage under the different ratios of interdigital electrode space and width is carried out when the UV power is given.The results show that when the ratio of interdigital electrode space and width（L/W） equals 1,the photocurrent tends to be at a maximum.

Synthesis and electrical characterization of tungsten oxide nanowires

Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition （CVD） method with vapour-solid （VS） mechanism.Tin powders are used to control oxygen concentration in the furnace,thereby assisting the growth of the tungsten oxide nanowires.The grown tungsten oxide nanowires are determined to be of crystalline W18O49. I-V curves are measured by an in situ transmission electron microscope （TEM） to investigate the electrical properties of the nanowires.All of the I-V curves observed are symmetric,which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I-V curves by using a metal semiconductor-metal （MSM） model give some intrinsic parameters of the tungsten oxide nanowires,such as the carrier concentration,the carrier mobility and the conductivity.

All-Fiber Liquid-Level Sensor Based on In-Line MSM Fiber Structure

We propose and demonstrate an all-fiber liquid-level sensor using an in-line multimode-single-mode-multimode (MSM) fiber structure. A piece of single-mode fiber (SMF) is spliced to two sections of equivalent multimode fiber (MMF) which are used as both mode splitter and mode coupler. The cladding mode will be excited when the light propagates from MMF to SMF, and then it will be combined with fundamental mode to form a Mach-Zehnder interferometer (MZI) when the light propagates from SMF to the other MMF. The liquid level is detected by the selected resonant dips shift of the transmission spectrum. A sensing sensitivity of 264.6 pm/mm is achieved for the proposed sensor with an SMF length of 26mm. Due to its compact structure, easy fabrication, and high sensitivity, the proposed liquid-level sensor is attractive for practical applications in a variety of fields, such as marine detection and chemical processing.

Two-dimensional numerical computation of the structure-dependent spectral response in a 4H-SiC metal-semiconductor-metal ultraviolet photodetector with consideration of reflection and absorption on contact electrodes

A two-dimensional model of a 4H-SiC metal-semiconductor-metal（MSM） ultraviolet photodetector has been established using a self-consistent numerical calculation method.The structure-dependent spectral response of a 4H-SiC MSM detector is calculated by solving Poisson＇s equation,the current continuity equation and the current density equation.The calculated results are verified with experimental data.With consideration of the reflection and absorption on the metal contacts,a detailed study involving various electrode heights（H）,spacings （S） and widths（W） reveals conclusive results in device design.The mechanisms responsible for variations of responsivity with those parameters are analyzed.The findings show that responsivity is inversely proportional to electrode height and is enhanced with an increase of electrode spacing and width.In addition,the ultraviolet （UV）-to-visible rejection ratio is 103.By optimizing the device structure at 10 V bias,a responsivity as high as 180.056 mA/W,a comparable quantum efficiency of 77.93%and a maximum UV-to-visible rejection ratio of 1875 are achieved with a detector size of H = 50 nm,S =9μm and W = 3μm.

Simulation and optimization of a 6H-SiC metal-semiconductor-metal ultraviolet photodetector

Based on thermionic emission theory,a model of a 6H-SiC metal-semiconductor-metal（MSM） ultraviolet photodetector is established with the simulation package ISE-TCAD.A device with 3μm electrode width（W） and 3μm electrode spacing（L） is simulated.The findings show that the MSM photodetector has quite a low dark current of 15 pA at 10V bias and the photocurrent is two orders of magnitude higher than the dark current.The influences of different structures on dark and illuminated current-voltage characteristics of the MSM photodetector are investigated to optimize the device parameters.Simulation results indicate that the maximum photocurrent and the highest ratio of photocurrent to dark current at 15 V bias are 5.3 nA and 327 with device parameters of W=6μm,L=3μm and W =3μm,L=6μm,respectively.