38 research outputs found
Leakage Current Mechanisms in SiGe HBTs Fabricated Using Selective and Nonselective Epitaxy
SiGe heterojunction bipolar transistors (HTBs) have been fabricated using selective epitaxy for the Si collector, followed in the same growth step by nonselective epitaxy for the p+ SiGe base and n-Si emitter cap. DC electrical characteristics are compared with cross-section TEM images to identify the mechanisms and origins of leakage currents associated with the epitaxy in two different types of transistor . In the first type, the polysilicon emitter is smaller than the collector active area, so that the extrinsic base implant penetrates into the single-crystal Si and SiGe around the perimeter of the emitter and the polycrystalline Si and SiGe exrtrinsic base. In these transistors, the Bummel plots are near-ideal and there is no evidence of emitter/collector leakage. In the second type, the collector active area is smaller than the polysilicon emitter, so the extrinsic base implant only penetrates into the polysilicon extrinsic base. In these transistors, the leakage currents observed depend on the base doping level. In transistors with a low doped base, emitter/collector and emitter/base leakage is observed, whereas in transistors with a high doped base only emitter/base leakage is observed. The emitter/collector leakage is explained by punch through o fhte base caused by thinning of the SiGe base at the emitter perimeter. The emitter/base leakeage is shown to be due to Poole-Frenkel mechanism and is explained by penetration of the emitter/base depletion region into the p+ polysilicon extrinsic base at the emitter periphery. Variable collector/base reverse leakage currents are observed and a variety of mechanisms are observed, including Shockley-Read-Hall recombination, trap assisted tunneling, Poole Frenkel and band to band tunneling. These result s are explained by the presence of polysilicon grains on the sidewalls of the field oxide at the collector perimeter
Activation energy for fluorine transport in amorphous silicon
The transport of ion implanted F in amorphous Si is studied using secondary ion mass spectroscopy and transmission electron microscopy. Significant redistribution of F is observed at temperatures in the range 600°C to 700°C. The measured F depth-profiles are modelled using a simple Gaussian solution to the diffusion equation, and the diffusion coefficient is deduced at each temperature. An activation energy of 2.2eV±0.4eV for F transport is extracted from an Arrhenius plot of the diffusion coefficients. It is shown that the F transport is influenced by implantation induced defects
Exploratory study of shrinkage of the diffraction cone for the generalized BFKL pomeron
In color dipole gBFKL dynamics, we describe the emerging gBFKL phenomenology
of a subasymptotic energy dependence of the diffraction slope and discuss
possibilities of testing the gBFKL predictions in exclusive photo- and
electroproduction of vector mesons at HERA. A substantial shrinkage of the
diffraction cone processes from the CERN/FNAL to
HERA range of energy is predicted. This subasymptotic shrinkage is faster
than expected from the small slope of pomeron's Regge trajectory
\alpha_{\Pom}'. We point out that the diffraction slope is a scaling function
of , what relates production of different vector mesons.Comment: plain LaTeX, 4 figures upon the request from
[email protected]
Hadronic sizes and observables in high-energy scattering
The functional dependence of the high-energy observables of total cross
section and slope parameter on the sizes of the colliding hadrons predicted by
the model of the stochastic vacuum and the corresponding relations used in the
geometric model of Povh and H\"ufner are confronted with the experimental data.
The existence of a universal term in the expression for the slope, due purely
to vacuum effects, independent of the energy and of the particular hadronic
system, is investigated. Accounting for the two independent correlation
functions of the QCD vacuum, we improve the simple and consistent description
given by the model of the stochastic vacuum to the high-energy pp and pbar-p
data, with a new determination of parameters of non-perturbative QCD. The
increase of the hadronic radii with the energy accounts for the energy
dependence of the observables.Comment: Latex, using Revtex.style . 2 ps figures. To be published in Physical
Review D , July 199
High Energy Hadron-Nucleus Cross Sections and Their Extrapolation to Cosmic Ray Energies
Old models of the scattering of composite systems based on the Glauber model
of multiple diffraction are applied to hadron-nucleus scattering. We obtain an
excellent fit with only two free parameters to the highest energy
hadron-nucleus data available. Because of the quality of the fit and the
simplicity of the model it is argued that it should continue to be reliable up
to the highest cosmic ray energies. Logarithmic extrapolations of proton-proton
and proton-antiproton data are used to calculate the proton-air cross sections
at very high energy. Finally, it is observed that if the exponential behavior
of the proton-antiproton diffraction peak continues into the few TeV energy
range it will violate partial wave unitarity. We propose a simple modification
that will guarantee unitarity throughout the cosmic ray energy region.Comment: 8 pages, 9 postscript figures. This manuscript replaces a partial
manuscript incorrectly submitte
Color Dipole Systematics of the Diffraction Slope in Diffractive Photo- and Electroproduction of Vector Mesons
We present the first evaluation of the color dipole diffraction slope from
the data on diffractive photo- and electroproduction of vector mesons. The
energy and dipole size dependence of the found dipole diffraction slope are
consistent with the color dipole gBFKL dynamics.Comment: 11 pages including 2 figure
A Transient New Coherent Condition of Matter: The Signal for New Physics in Hadronic Diffractive Scattering
We demonstrate the existence of an anomalous structure in the data on the
diffractive elastic scattering of hadrons at high energies and small momentum
transfer. We analyze five sets of experimental data on
scattering from five different experiments with colliding beams, ranging from
the first-- and second--generation experiments at GeV to the
most recent experiments at 546 GeV and at 1800 GeV. All of the data sets
exhibit a localized anomalous structure in momentum transfer. We represent the
anomalous behavior by a phenomenological formula. This is based upon the idea
that a transient coherent condition of matter occurs in some of the
intermediate inelastic states which give rise, via unitarity, to diffractive
elastic scattering. The Fourier--Bessel transform into momentum--transfer space
of a spatial oscillatory behavior of matter in the impact--parameter plane
results in a small piece of the diffractive amplitude which exhibits a
localized anomalous behavior near a definite value of . In addition, we
emphasize possible signals coming directly from such a new condition of matter
that may be present in current experiments on inelastic processes.Comment: 25 pages, LaTeX (12 figures, not included). A complete postscript
file (except figures 1 and 11, which are available upon request) is available
via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as
/ttp94-03 /ttp94-03.ps, Local preprint# TTP94-03 (March 1994
The Wave Function of 2S Radially Excited Vector Mesons from Data for Diffraction Slope
In the color dipole gBFKL dynamics we predict a strikingly different Q^2 and
energy dependence of the diffraction slope for the elastic production of ground
state V(1S) and radially excited V'(2S) light vector mesons. The color dipole
model predictions for the diffraction slope for \rho^0 and \phi^0 production
are in a good agreement with the data from the fixed target and collider HERA
experiments. We present how a different form of anomalous energy and Q^2
dependence of the diffraction slope for V'(2S) production leads to a different
position of the node in radial wave function and discuss a possibility how to
determine this position from the fixed target and HERA data.Comment: 20 pages and 6 figures. Title change
Non-Perturbative QCD Treatment of High-Energy Hadron-Hadron Scattering
Total cross-sections and logarithmic slopes of the elastic scattering
cross-sections for different hadronic processes are calculated in the framework
of the model of the stochastic vacuum. The relevant parameters of this model, a
correlation length and the gluon condensate, are determined from scattering
data, and found to be in very good agreement with values coming from completely
different sources of information. A parameter-free relation is given between
total cross-sections and slope parameters, which is shown to be remarkably
valid up to the highest energies for which data exist.Comment: 60 pages, Heidelberg preprin