232 research outputs found
Effect of long-range Coulomb interaction on shot-noise suppression in ballistic transport
We present a microscopic analysis of shot-noise suppression due to long-range
Coulomb interaction in semiconductor devices under ballistic transport
conditions. An ensemble Monte Carlo simulator self-consistently coupled with a
Poisson solver is used for the calculations. A wide range of injection-rate
densities leading to different degrees of suppression is investigated. A sharp
tendency of noise suppression at increasing injection densities is found to
scale with a dimensionless Debye length related to the importance of
space-charge effects in the structure.Comment: RevTex, 4 pages, 4 figures, minor correction
Unipolar transport and shot noise in metal-semiconductor-metal structures
We carry out a self-consistent analytical theory of unipolar current and
noise properties of metal-semiconductor-metal structures made of highly
resistive semiconductors in the presence of an applied bias of arbitrary
strength. By including the effects of the diffusion current we succeed to study
the whole range of carrier injection conditions going from low level injection,
where the structure behaves as a linear resistor, to high level injection,
where the structure behaves as a space charge limited diode. We show that these
structures display shot noise at the highest voltages. Remarkably the crossover
from Nyquist noise to shot noise exhibits a complicate behavior with increasing
current where an initial square root dependence (double thermal noise) is
followed by a cubic power law.Comment: 10 pages, 8 figures. Accepted for publication in Journal of Applied
Physics (Scheduled 1 January 2003
Amplification by stochastic interference
A new method is introduced to obtain a strong signal by the interference of
weak signals in noisy channels. The method is based on the interference of 1/f
noise from parallel channels. One realization of stochastic interference is the
auditory nervous system. Stochastic interference may have broad potential
applications in the information transmission by parallel noisy channels
Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon
We present a microscopic theory of the low-frequency voltage noise (known as
"1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This
theory traces the noise back to the long-range fluctuations of the Coulomb
potential produced by deep defects, thereby predicting the absolute noise
intensity as a function of the distribution of defect activation energies. The
predictions of this theory are in very good agreement with our own experiments
in terms of both the absolute intensity and the temperature dependence of the
noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added,
but no conceptual revision
Noise suppression by noise
We have analyzed the interplay between an externally added noise and the
intrinsic noise of systems that relax fast towards a stationary state, and
found that increasing the intensity of the external noise can reduce the total
noise of the system. We have established a general criterion for the appearance
of this phenomenon and discussed two examples in detail.Comment: 4 pages, 4 figure
Shot noise suppression in multimode ballistic Fermi conductors
We have derived a general formula describing current noise in multimode
ballistic channels connecting source and drain electrodes with Fermi electron
gas. In particular (at ), the expression describes the
nonequilibrium ''shot'' noise, which may be suppressed by both Fermi
correlations and space charge screening. The general formula has been applied
to an approximate model of a 2D nanoscale, ballistic MOSFET. At large negative
gate voltages, when the density of electrons in the channel is small, shot
noise spectral density approaches the Schottky value , where
is the average current. However, at positive gate voltages, when the
maximum potential energy in the channel is below the Fermi level of the
electron source, the noise can be at least an order of magnitude smaller than
the Schottky value, mostly due to Fermi effects.Comment: 4 page
Stochastic Resonance in Noisy Non-Dynamical Systems
We have analyzed the effects of the addition of external noise to
non-dynamical systems displaying intrinsic noise, and established general
conditions under which stochastic resonance appears. The criterion we have
found may be applied to a wide class of non-dynamical systems, covering
situations of different nature. Some particular examples are discussed in
detail.Comment: 4 pages, RevTex, 3 PostScript figures available upon reques
- …