32 research outputs found
Theory of traveling filaments in bistable semiconductor structures
We present a generic nonlinear model for current filamentation in
semiconductor structures with S-shaped current-voltage characteristics. The
model accounts for Joule self-heating of a current density filament. It is
shown that the self-heating leads to a bifurcation from static to traveling
filament. Filaments start to travel when increase of the lattice temperature
has negative impact on the cathode-anode transport. Since the impact ionization
rate decreases with temperature, this occurs for a wide class of semiconductor
systems whose bistability is due to the avalanche impact ionization. We develop
an analytical theory of traveling filaments which reveals the mechanism of
filament motion, find the condition for bifurcation to traveling filament, and
determine the filament velocity.Comment: 13 pages, 5 figure
Pattern Formation in Semiconductors
In semiconductors, nonlinear generation and recombination processes of free carriers and nonlinear charge transport can give rise to non-equilibrium phase transitions. At low temperatures, the basic nonlinearity is due to the autocatalytic generation of free carriers by impact ionization of shallow impurities. The electric field accelerates free electrons, causing an abrupt increase in free carrier density at a critical electric field. In static electric fields, this nonlinearity is known to yield complex filamentary current patterns bound to electric contacts
Self-organization patterns in electroluminescence of bistable ZnS:Mn thin-film structures
An overview of recent original results concerning self-organized pattern formation in the emission of bistable alternating current ZnS:Mn thin - film electroluminescent structures (TFELS) as a dissipative system is given. The influence of technological factors, affecting the properties TFELS, and driving conditions on both the patterns and the hysteresis of the charge- voltage dependence that is responsible for bistability of the TFELS are considered. The correlation between patterns and the shape of the hysteresis is analyzed. The physical processes with positive and negative feedback, which serve, respectively, as activator and inhibitor in the given dissipative system, are discussed
General theory of instabilities for patterns with sharp interfaces in reaction-diffusion systems
An asymptotic method for finding instabilities of arbitrary -dimensional
large-amplitude patterns in a wide class of reaction-diffusion systems is
presented. The complete stability analysis of 2- and 3-dimensional localized
patterns is carried out. It is shown that in the considered class of systems
the criteria for different types of instabilities are universal. The specific
nonlinearities enter the criteria only via three numerical constants of order
one. The performed analysis explains the self-organization scenarios observed
in the recent experiments and numerical simulations of some concrete
reaction-diffusion systems.Comment: 21 pages (RevTeX), 8 figures (Postscript). To appear in Phys. Rev. E
(April 1st, 1996
Regenerative memory in time-delayed neuromorphic photonic resonators
We investigate a photonic regenerative memory based upon a neuromorphic oscillator with a delayed self-feedback (autaptic) connection. We disclose the existence of a unique temporal response characteristic of localized structures enabling an ideal support for bits in an optical buffer memory for storage and reshaping of data information. We link our experimental implementation, based upon a nanoscale nonlinear resonant tunneling diode driving a laser, to the paradigm of neuronal activity, the FitzHugh-Nagumo model with delayed feedback. This proof-of-concept photonic regenerative memory might constitute a building block for a new class of neuron-inspired photonic memories that can handle high bit-rate optical signals
IBIC analysis of high-power devices
10.1016/S0168-583X(01)00487-6Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms1811-4311-314NIMB
Stoßionisationsinduzierte Strukturbildung in Halbleitern mittels Mikrowellen
In gering dotierten Halbleiterschichten kann bei elektrischen Feldern von wenigen V/cm ein Nichtgleichgewichtsphasenübergang von einem niedrigleitenden in einen hochleitenden Zustand beobachtet werden. Bei Beschaltung mit elektrischen Gleichfeldern ist dieser Übergang mit der Ausbildung von Stromfilamenten verbunden. Erstmals wurde auch ohne elektrische Kontakte, im elektrischen Wechselfeld von Mikrowellen, die Ausbildung kreisförmiger räumlichen Strukturen in der Elektronendichte gefunden. In Abhängigkeit von der Mikrowellenleistung tritt eine deutliche Hysterese im Entstehungs- und Verlöschprozeß der mikrowelleninduzierten Strukturen auf. Die Abstände der Strukturen werden mit den Ergebnissen zweidimensionaler Berechnungen der Mikrowellenfeldverteilung verglichen
Ion beam induced charge microscopy studies of power diodes
10.1088/0953-8984/16/2/007Journal of Physics Condensed Matter162S57-S66JCOM
Modeling of deep buried structures in high-power devices based on proton beam induced charge microscopy
10.1016/S0168-583X(03)01022-XNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms210164-168NIMB