High-Speed, High-Sensitivity Optoelectronic Device with Bilayer Electron and Hole Charge Plasma

Analogous to a drop exciting a wave in a reservoir that is detected more rapidly than the drop's transport by current flow, charge plasma confined in a semiconductor can transfer energy, hence respond much faster than the electric field-induced carrier drift current. Here we construct an optoelectronic device in which charge reservoirs respond to excitation with a speed that is impossible to achieve by transport of charge. In response to short optical pulses, this device produces electrical pulses that are almost 2 orders of magnitude shorter than the same device without the charge reservoirs. In addition to speed, the sensitivity of this process allowed us to measure, at room temperature, as low as 11 000 photons. These micro plasma devices can have a range of application such as optical communication with a fraction of a microwatt power compared to the present tens of milliwatts, ultrasensitive light detection with cryogenic cooling, photovoltaic devices capable of harvesting dim light, THz radiation detectors, and charged particle detectors

Enhanced Raman scattering from individual semiconductor nanocones and nanowires

Physical Review Letters, 96(15): pp. 4.We report strong enhancement (similar to 10(3)) of the spontaneous Raman scattering from individual silicon nanowires and nanocones as compared with bulk Si. The observed enhancement is diameter (d), excitation wavelength (lambda(laser)), and incident polarization state dependent, and is explained in terms of a resonant behavior involving incident electromagnetic radiation and the structural dielectric cross section. The variation of the Raman enhancement with d, lambda(laser), and polarization is shown to be in good agreement with model calculations of scattering from an infinite dielectric cylinder

Supporting information for: "Instability and transport of metal catalyst in the growth of tapered silicon nanowires"

Nano Letters, 6(9): pp. 1852-1857. http://dx.doi.org/10.1021/nl060533rDuring metal-catalyzed growth of tapered silicon nanowires, or silicon nanocones (SiNCs), Au-Si eutectic particles are seen to undergo significant and reproducible reductions in their diameters. The reductions are accompanied by the transfer of eutectic droplet mass to adjacent, initially metal catalyst-free substrates, producing secondary nucleation and growth of SiNCs. Remarkably, the catalyst particle diameters on the SiNCs grown on the adjacent substrates are strongly correlated with those on the SiNCs grown on the initially Au-nanoparticle-coated substrate. These post-growth nanoparticle sizes depend on temperature and are found to be independent of the initial nanoparticle sizes. Our modeling and analysis indicates that the size reduction and mass transfer could be explained by electrostatic charge-induced dissociation of the droplet. The reduction in size enables the controlled growth of SiNCs with tip sharpnesses approaching the atomic scale, indicating that metal-catalyst nanoparticles can play an even more dynamic role than previously thought, and suggesting additional modes of control of shape, and of nucleation and growth location

Optically modulated high-sensitivity heterostructure varactor

IEEE Electron Device Letters, 27(9): pp. 710-712.A novel optically modulated high-sensitivity heterostructure varactor, demonstrated as a strong candidate for high-order frequency-multiplier applications, is reported. The device is a δ modulation-doped heterostructure of AlGaAs/GaAs with two Schottky contacts on the top. The capacitance–voltage (C–V ) measurements show a Cmax/Cmin ratio up to 113 and an extremely high nonlinearity during the transition from high to low capacitance with sensitivity of up to 35. These results are one of the best obtained so far among similar structure devices. In addition, optoelectronic experimental results demonstrate that the slope of the C–V relationship can be modulated by the intensity of the incident optical power. A model describing the source of the reported C–V results is proposed along with the simulation results verifying the observed C–V behavior

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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Photodetectors : materials, devices and applications /

AnnotationCIP data; item not viewed.""Front Cover""; ""Photodetectors""; ""Copyright Page""; ""Dedication""; ""Contents""; ""List of Contributors""; ""Preface""; ""Woodhead Publishing Series in Electronic and Optical Materials""; ""I. Materials, Detector Types and Devices""; ""1 Photodetectors for silicon photonic integrated circuits""; ""1.1 Introduction""; ""1.2 Technology""; ""1.2.1 Germanium""; ""1.2.2 Hybrid III/V-silicon""; ""1.2.3 Other technologies""; ""1.3 Optical properties of Si-based WGPDs""; ""1.4 Demonstrated waveguide photodiodes on silicon""; ""1.4.1 Vertically coupled PIN photodiodes in Si/Ge and InGaAs""""1.4.2 Butt-coupled PIN photodiodes in Ge""""1.4.3 MSM photodetectors""; ""1.4.4 SACM avalanche photodiodes""; ""1.4.5 Si/Ge UTC photodiodes""; ""1.4.6 Hybrid III/V-silicon UTC photodiodes""; ""1.5 Conclusions and future outlook""; ""References""; ""2 High-speed high-sensitivity low power photodetector with electron and hole charge plasma""; ""2.1 Introduction""; ""2.2 Device structure""; ""2.3 Current-voltage relationship""; ""2.4 Time response""; ""2.4.1 Components of total temporal response""; ""2.5 Analysis and modeling""; ""2.6 Conclusions""; ""References""""3 Carbon nanotube and graphene photonic devices""""3.1 Introduction""; ""3.2 Nonlinearity of carbon nanotubes and graphene; saturable absorption""; ""3.2.1 Nonlinear saturable absorption in SWNTs and graphene""; ""3.2.2 Conventional SWNT mode-lockers and fiber-pulsed lasers""; ""3.3 Novel interaction schemes of propagating light with carbon nanostructures""; ""3.3.1 SWNT-deposited side-polished fibers as mode-lockers""; ""3.3.2 Aligned SWNTs on side-polished fibers""; ""3.3.3 High-energy pulse formation with SWNTs on side-polished fibers""""3.3.4 High-energy pulse formation with graphene""""3.3.5 SWNTs coated around tapered fibers""; ""3.4 Highly efficient preparation of fiber mode-lockers""; ""3.4.1 Electrospray of SWNTs""; ""3.4.2 Aerosol deposition for SWNT hosting into SiO2""; ""3.4.3 Optical deposition of graphene/polyvinyl acetate (PVAc)""; ""3.4.4 Mechanically exfoliated graphene""; ""3.5 Conclusion""; ""References""; ""4 Nanowire enabled photodetection""; ""4.1 Introduction""; ""4.2 NW PD fabrication themes""; ""4.2.1 Direct NW integration""; ""4.2.2 Transfer-printing/pick-and-place techniques""""4.2.3 Transfer printing of horizontally oriented semiconductor NWs""""4.3 Recent device demonstrations""; ""4.3.1 Demonstrations of direct growth PDs""; ""4.3.2 Waveguide coupled PDs""; ""4.3.3 Plasmonic PDs""; ""4.3.4 Photoactive oxide devices""; ""4.4 Device design challenges""; ""4.4.1 Impediments on contact formation""; ""4.4.2 Hybrid contacts for print transferred NWs""; ""4.4.3 Control of NW doping""; ""4.4.4 NW photo-trapping enhancement""; ""4.4.5 Additional challenges""; ""4.5 Towards development of integrated multispectral NW PDs""; ""4.6 Conclusions and perspectives""AnnotationElsevie

Nanowire Optoelectronics

Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs), lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in “volumetric modes,”which have so far been presented in terms of Fabry–Perot (FP), and helical resonance modes. We report on finite-difference timedomain (FDTD) simulations with the aim of identifying the dependence of these modes on geometry (length, width), tapering, shape (cylindrical, hexagonal), core–shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs) form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption) and downward transitions (emission) of light inNWs; rather, the electronic transition rates should be considered. We discuss this “rate management” scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs) that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures

To appear in the Journal of Supercomputing

A scalable interconnection network architecture for petaflops computing b

Volterra Series Analysis and Synthesis of a Neural Network for Velocity Estimation

The motion detection problem occurs frequently in many applications connected with computer vision. Researchers have studied motion detection based on naturally occurring biological circuits for over a century. In this paper, we propose and analyze a motion detection circuit which is based on nerve membrane conduction. It consists of two unidirectional neural networks connected in an opposing fashion. Volterra input--output (I--O) models are then derived for the network so that velocity estimation can be cast as a parameter estimation problem. The technique is demonstrated through simulation. Index Terms---Image motion analysis, neural network architecture, nonlinear systems, parameter estimation, Volterra series. I. INTRODUCTION T HE SYSTEMATIC study of motion detection schemes and their underlying biological circuitry is over a century old [1], [2]. Researchers have studied motion detection either based on physiological units responding differently to movement in different direct..

Volterra Series Analysis of a Neural Network for Velocity Estimation

2. THE MOTION DETECTION MODEL In this paper we propose and analyze a motion detection Neural networks that are based on modulation of concircuit which is based on nerve membrane conduction. It ductance of nerve membranes by other cells of the network consists of two unidirectional neural networks connected have been studied extensively and found to have widely in an opposing fashion. Volterra input-output models are varied and complex computational properties such as then derived for the network so that the velocity estimacontrast enhancement, dynamic range compression, and tion can then be cast as a parameter estimation problem. adaptation to mean input levels (for a review see [11, 12]). The technique is demonstrated through simulation. The elementary shunting motion detector (ESMD) is an intensity, or luminescence, based scheme of short range 1. INTRODUCTION motion detection based on the mechanism of shunting inhibition [13, 14]. It consists of two subsystems, each being The syste..