1,721,083 research outputs found
Physically-based analytical model for a-Si devices including drift and diffusion currents
No full textComprehensive system for submicron-device simulation
No full textWe present here a comprehensive system for submicron-device simulation based on the hydrodynamic (HD) model and the expansion of the Boltzmann equation (BTE) in spherical harmonics (SHE). In the typical operating regime of semiconductor devices, the accurate calculation of the carrier concentration and velocity, along with the information about the carrier temperature, provided by the HD model, is important for describing a number of phenomena indicated by the general term hot-carrier effects, which play a relevant role in modern devices. The coefficients of the model are computed by adopting the solution method for the BTE based on the SHE, and using the full-band structure for both the electron and valence band of silicon. The dependence of the coefficients on lattice temperature has been investigated and compared with available experimental data
Transport scaling limits of ovonic Devices: a simulative approach
Full text linkThe transport scaling limits of Ovonic devices are studied by means of a numerical solution of a time- and space-dependent transport models based on a set of equations that provide a good physical grasp of the microscopic process at hand. The predictivity of the approach has been confirmed through the comparison with recent experimental results where the parasitic effects have been reduced by the use of top-technology measuring equipments. The present analysis is performed for the AgInSbTe chalcogenide, since this material exibits a steep threshold-switching dynamics which makes it promising for high-speed non-volatile memory applications
A fifth-order method for 1D device solution
No full textThe so called Numerov process provides an inexpensive, accurate discretization scheme for second-order equations. In this paper the Numerov process has been made applicable to practical cases with typical applications to numerical solution of the coupled Schroedinger Poisson equations. Here the feasibility of the 5-th order method is proved for the longitudinal part of the wave equation
A Coherent Extension of the Transport Equations in Semiconductors Incorporating the Quantum Correction: Part II – Collective Transport
No full textThe aim of this investigation is to consistently incorporate quantum corrections in the transport model for applications to nanoscale semiconductor devices. This paper is made of two parts. In Part I, a set of two semiclassical equations were derived, in which the dynamics of the dispersion of the single-particle wave function is accounted for in addition to that of the expectation value of position. The model is founded on an approximate description of the wave function that eliminates the need for the Ehrenfest approximation. This leads to a set of two Newton-like single-particle equations for position and dispersion. Here, in Part II, it is shown that the Lagrangian form of the single-particle equations naturally lends itself to the incorporation of such extended dynamics into the statistical framework. The theory is suitable for different levels of applications: description of the single-particle ballistic dynamics, solution of the generalized Boltzmann equation by Monte Carlo or other methods, and solution of the continuity equations in the position-dispersion space
Adaptive K-NN for the detection of air pollutants with a sensor array
No full textThe field of air-quality monitoring is gaining increasing interest, with regard to both indoor environment and air-pollution control in open space. This work introduces a pattern recognition technique based on adaptive K-nn applied to a multisensor system, optimized for the recognition of some relevant tracers for air pollution in outdoor environment, namely benzene, toluene, and xylene (BTX), NO/sub 2/, and CO. The pattern-recognition technique employed aims at recognizing the target gases within an air sample of unknown composition and at estimating their concentrations. It is based on PCA and K-nn classification with an adaptive vote technique based on the gas concentrations of the training samples associated to the K-neighbors. The system is tested in a controlled environment composed of synthetic air with a fixed humidity rate (30%) at concentrations in the ppm range for BTX and NO/sub 2/, in the range of 10 ppm for CO. The pattern recognition technique is experimented on a knowledge base composed of a limited number of samples (130), with the adoption of a leave-one-out procedure in order to estimate the classification probability. In these conditions, the system demonstrates the capability to recognize the presence of the target gases in controlled conditions with a high hit-rate. Moreover, the concentrations of the individual components of the test samples are successfully estimated for BTX and NO/sub 2/ in more than 80% of the considered cases, while a lower hit-rate (69%) is reached for CO
Intrinsic Electric Oscillations of Ovonic Devices towards the TeraHerz limit
No full textThe time-dependent response of Ovonic devices to an electric potential ramp signal
is analysed by means of an enhanced version of a previously published time-dependent charge-
transport model proposed by the authors. Depending on the inevitable parasitics of the system,
either stable or oscillating solutions are found according to the position of the load line. The
model also allows for speculations on the potential of Ovonic materials in the design of high-
frequency oscillating circuits close to the terahertz range
A Coherent Extension of the Transport Equations in Semiconductors Incorporating the Quantum Correction: Part I – Single Particle Dynamics
No full textThe aim of the investigation is to consistently incorporate quantum corrections in the transport model for applications to nanoscale semiconductor devices. This paper is comprised of two parts. Part I derives a set of two semiclassical equations in which the dynamics of the dispersion of the single-particle wave function is accounted for in addition to that of the expectation value of position. The model is founded on an approximate description of the wave function that eliminates the need of the Ehrenfest approximation. This leads to a set of two Newton-like single-particle equations for position and dispersion. In Part II, it will be shown that the Lagrangian form of the single-particle equations naturally lends itself to the incorporation of such extended dynamics into the statistical framework. The theory is suitable for different levels of applications: description of the single-particle ballistic dynamics, solution of the generalized Boltzmann equation by the Monte Carlo method or other methods, and solution of the continuity equations in the position-dispersion space
Implementing physical unclonable functions using PCM arrays
Full text linkThe stochastic nature of the switching mechanism of amorphous phase-change memory (PCM) arrays can fruitfully be exploited to implement primitives for hardware security. This paper tackles, by means of PCM, the feasibility of Reconfigurable Physical Unclonable Functions, that constitute one of the two building blocks of cryptographic applications
An improved MPPT algorithm based on hybrid RCC scheme for single-phase PV systems
No full textSingle-stage H-bridge grid-connected inverters are considered as a simple, compact, and economic topology compared with double-stage converters. A maximum power point tracking (MPPT) control is necessary in photovoltaic (PV) generation system to extract maximum power from the PV arrays. Many MPPT techniques have been proposed and discussed in the literature. Among them, the ripple correlation control (RCC) algorithm is fast and effective, particularly suitable for single-phase configurations since it uses as perturbation the embedded oscillation of dc current and dc voltage at twice of grid frequency (e.g., 100 Hz). The main drawback of this method is the unstable behavior during sudden variation of sun irradiance, where the conventional RCC gives wrong estimation of the power derivative (dP/dV), causing wide dc voltage and dc current overshoots. To overcome this problem, a hybrid RCC-constant voltage regulator algorithm combined to a high-peformance dq grid current controller is proposed to improve the transient performance. The whole grid-connected photovoltaic generation scheme has been implemented numerically by MATLAB/Simulink, verifying steady-state and dynamic performances under different sun irradiance transients. The comparison with the corresponding behavior of a standard RCC algorithm emphasized the effectiveness of the proposed hybrid RCC controller
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