• Title, Summary, Keyword: Boundary potential barrier

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A New Two-Dimensional Model for the Drain-Induced Barrier Lowering of Fully Depleted Short-Channel SOI-MESFET's

  • Jit, S.;Pandey, Prashant;Pal, B.B.
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.3 no.4
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    • pp.217-222
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    • 2003
  • A new two-dimensional analytical model for the potential distribution and drain-induced barrier lowering (DIBL) effect of fully depleted short-channel Silicon-on-insulator (SOI)-MESFET's has been presented in this paper. The two dimensional potential distribution functions in the active layer of the device is approximated as a simple parabolic function and the two-dimensional Poisson's equation has been solved with suitable boundary conditions to obtain the bottom potential at the Si/oxide layer interface. It is observed that for the SOI-MESFET's, as the gate-length is decreased below a certain limit, the bottom potential is increased and thus the channel barrier between the drain and source is reduced. The similar effect may also be observed by increasing the drain-source voltage if the device is operated in the near threshold or sub-threshold region. This is an electrostatic effect known as the drain-induced barrier lowering (DIBL) in the short-gate SOI-MESFET's. The model has been verified by comparing the results with that of the simulated one obtained by solving the 2-D Poisson's equation numerically by using the pde toolbox of the widely used software MATLAB.

Dependence of Optical Matrix Elements on the Boundary Conditions of the Continuum States in Quantum Wells

  • Jang Y. R.;Yoo K. H.;Ram-Mohan L. R.
    • Journal of the Optical Society of Korea
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    • v.9 no.2
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    • pp.39-44
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    • 2005
  • Unlike for the bound states, several different boundary conditions are used for the continuum states above the barrier in semiconductor quantum wells. We employed three boundary conditions, infinite potential barrier boundary condition, periodic boundary condition and scattering boundary condition, and calculated the local number of states, wavefunctions and optical matrix elements for the symmetric and asymmetric quantum wells. We discussed how these quantities are related in the three boundary conditions. We argue that the scattering boundary condition has several advantages over the other two cases. These results would be useful in understanding quantum well lasers and detectors involving continuum states.

Effects of Grain Boundaries on Photovoltaic Current and Photoinduced Domain Switching in Ferroelectric Ceramics

  • Kim, Sung-Ryul;Choi, Dong-Gu;Choi, Si-Kyung
    • The Korean Journal of Ceramics
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    • v.6 no.3
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    • pp.262-266
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    • 2000
  • We investigated the effect of the grain size on the photovoltaic current in (Pb$_{1-x}$La$_x$)TiO$_3$ceramics, and the photoinduced domain switching in (Pb$_{0.85}$La$_{0.15}$)TiO$_3$and BaTiO$_3$ceramics. These behaviors in ferroelectric ceramics were attributed to the grain boundary at which photoexcited electrons were trapped. As the charged grain boundary acted as an electro-potential barrier which impeded the movement of electrons, the photovoltaic current showed a peak at a critical grain size. The space charge field built by the electrons trapped at the grain bound-aries was accounted for the photoinduced domain switching, and AE experimental results support well this account.

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Grain Boundary Chemistry and Electrical Characteristics of Semiconducting $SrTiO_3$ Ceramics Synthesized from Surface-Coated Powders (표면 코팅된 분말을 이용하여 제조된 반도성 $SrTiO_3$ 소결체의 입계화학과 전기적 특성)

  • Park, Myung-Beom;Kim, Chong-Don;Heo, Hyun;Cho, Nam-Hee
    • Journal of the Korean Ceramic Society
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    • v.36 no.11
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    • pp.1252-1260
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    • 1999
  • The defect chemistry and electrical characteristics of the grain boundaries of semiconducting SrTiO3 ceramics synthesized with wet-chemically surface-coated powders were investigated. The starting powders were separated into groups of 1-10${\mu}{\textrm}{m}$ 10-20${\mu}{\textrm}{m}$ etc by sedimentation and sieving methods. Na+ ions were absorbed on the powder surfaces by wet chemical-treatment method. The width of the grain boundary ranged up to several nm and the intergranular materials was amorphous. The additives coated on the surface of the powders were observed to be present at the grain boundaries of the ceramics. The diffusion depth of the additives into grains was about 30nm for the SrTiO3 ceramics synthesized with 5w/o coated materials, The threshold voltage grain boundary resistance and boundary potential barrier of the ceramics increased from 0.67V/cm 2.27k$\Omega$ and 0.05eV to 80.9V/cm 13.0k$\Omega$ 1.44eV with increasing the amount of the additives from 0 to 5 w/o respectively .

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Electrical Characteristics of (BaSr)TiO3-based PTCR Devices under the Electric Field

  • Lee, Joon-Hyung;Cho, Sang-Hee
    • Journal of the Korean Ceramic Society
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    • v.39 no.1
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    • pp.16-20
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    • 2002
  • Semiconducting (Ba.Sr)TiO$_3$ceramic device, which shows the PTCR effect, has been usually used as a current limiter. In this case, the device should endure the condition under the high electric field. In this study, the dynamic electrical properties of the PTCR device under high voltage has been evaluated. Two different formulated powders were used and the sintered bodies exhibited the different grain size and porosity. The wide range of characterization such as complex impedance spectroscopy, microstructure, I-V characteristics and voltage dependence of resistivity of the samples were performed. The PTCR effect of the specimen containing coarse grains was very sensitively dependent on the AC electric field, showing that it was inversely pro-portional to the grain boundary potential barrier. The withstanding voltage was proportional to the potential barrier of grain boundary.

A 2-D Model for the Potential Distribution and Threshold Voltage of Fully Depleted Short-Channel Ion-Implanted Silicon MESFET's

  • Jit, S.;Morarka, Saurabh;Mishra, Saurabh
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.5 no.3
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    • pp.173-181
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    • 2005
  • A new two dimensional (2-D) model for the potential distribution of fully depleted short-channel ion-implanted silicon MESFET's has been presented in this paper. The solution of the 2-D Poisson's equation has been considered as the superposition of the solutions of 1-D Poisson's equation in the lateral direction and the 2-D homogeneous Laplace equation with suitable boundary conditions. The minimum bottom potential at the interface of the depletion region due to the metal-semiconductor junction at the Schottky gate and depletion region due to the substrate-channel junction has been used to investigate the drain-induced barrier lowering (DIBL) and its effects on the threshold voltage of the device. Numerical results have been presented for the potential distribution and threshold voltage for different parameters such as the channel length, drain-source voltage, and implanted-dose and silicon film thickness.

Electrical Properties of Pr-doped ZnO Varistors (Pr-첨가 ZnO 바리스터의 전기적 특성)

  • 곽민환;이상기;조성걸
    • Journal of the Korean Ceramic Society
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    • v.34 no.12
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    • pp.1275-1281
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    • 1997
  • ZnO varistors containing 5.0 at% Co3O4 and Pr6O11, ranging from 0.1 to 1.0 at%, were sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$. The I-V characteristics and nonlinear coefficients of the specimens were investigated with respect to Pr addition and sintering temperature. In general the specimens sintered at 130$0^{\circ}C$ showed better varistor characteristic than those fired at 135$0^{\circ}C$, which seemed to be related with the liquid phase formation during sintering. The barrier heights obtained from C-V relations, 0.29-1.36 eV, were different from those acquired using resistivity-temperature plots measured at low voltage per grain boundary. Therefore the estimation of potential barrier heights using C-V relations is better suited for the specimens prepared in this study. The carrier densities obtained using C-V relations were ~1018 cm-3.

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Poly-crystalline Silicon Thin Film Transistor: a Two-dimensional Threshold Voltage Analysis using Green's Function Approach

  • Sehgal, Amit;Mangla, Tina;Gupta, Mridula;Gupta, R.S.
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.7 no.4
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    • pp.287-298
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    • 2007
  • A two-dimensional treatment of the potential distribution under the depletion approximation is presented for poly-crystalline silicon thin film transistors. Green's function approach is adopted to solve the two-dimensional Poisson's equation. The solution for the potential distribution is derived using Neumann's boundary condition at the silicon-silicon di-oxide interface. The developed model gives insight into device behavior due to the effects of traps and grain-boundaries. Also short-channel effects and drain induced barrier lowering effects are incorporated in the model. The potential distribution and electric field variation with various device parameters is shown. An analysis of threshold voltage is also presented. The results obtained show good agreement with simulated results and numerical modeling based on the finite difference method, thus demonstrating the validity of our model.

Analysis on Metal Contact Resistance and Grain Boundary Barrier Height of Ceramic PTC Thermistor (Ceramic PTC thermistor의 금속접촉저항과 입계전위장벽)

  • Jeon, Yong-Woo;Lim, Byung-Jae;Hong, Sang-Jin;Soh, Dea-Wha
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.235-236
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    • 2006
  • The contact resistance and grain boundary potential barrier of ceramic $BaTiO_3$ PTCR were investigated. The electroless plated Ni, evaporated Al, and Ag paste were chosen as electrode materials of PTCR device for comparison analysis before and after heat treatment. The contact resistance of electrode were measured by electrometer (dc), digital multimeter (dc), and LCR meter (ac). In the case of Al electroded samples, the heat treatment and protective oxide layer had high resistance and effect on the stability of PTCR effect against contact resistance degradation, but the Ag-paste had comparably high contact resistance before heat treatment and decreased after heat treatment with safe. On the other hand, the samples with electroless plated Ni electrode had good properties of contact resistance against aging.

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An Analysis of the Protective Potential Distribution against Corrosion for Hull ICCP with Computer simulation (컴퓨터 Simulation을 통한 선체 음극방식(ICCP)의 방식전위분포해석)

  • Im, Gwan-Jin;Kim, Ki-Joon;Lee, Myung-Hoon;Moon, Kyung-Man
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.395-400
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    • 2005
  • The ship hull part is always exposed to severe corrosive environments. Therefore, it should be protected in appropriate ways to reduce corrosion problems. So there are two effective methods in order to protect the corrosion of ship hull. One is the paint coating as a barrier between steel and electrolyte (seawater) and the other is the cathodic protection(CP) supplying protection current. In the conventional design process of the cathodic protection system the required current densities of protected materials have been used. However, the anode position of field or laboratory experiment for obtaining the required current density for CP is significantly different from anode position for real structures. Therefore, the recent CP design must consider the optimum anode position for potential distribution equally over the ship hull. The CP design companies in the advanced countries can obtain the potential distribution results on the cathodic materials by using the computer analysis module. This study would show how to approach the potential analysis in the field of corrosion engineering. The computer program can predict the under protection area on the structure when the boundary condition and analysis procedure are reasonable. In this analysis the polarization curve is converted to the boundary condition in material data.

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