scholarly journals Hierarchy of Full Band Structure Models for Monte Carlo Simulation

VLSI Design ◽  
1998 ◽  
Vol 6 (1-4) ◽  
pp. 147-153 ◽  
Author(s):  
U. Ravaioli ◽  
A. Duncan ◽  
A. Pacelli ◽  
C. Wordelman ◽  
K. Hess
Keyword(s):  
Monte Carlo ◽  
Band Structure ◽  
Computationally Efficient ◽  
Average Value ◽  
Scattering Rate ◽  
Numerical Noise ◽  
The Monte Carlo Method ◽  
Full Band ◽  
Scattering Anisotropy ◽  
Full Band Structure

This paper discusses the various hierarchy levels that are possible when the full band structure is considered. At the highest level, the scatterings are treated using complete k-k’ transition rates, which entail extremely memory intensive computational applications. At the lowest level, the scattering anisotropy is neglected and the scattering rate is considered to be a constant average value on energy isosurfaces of the bandstructure. This model is more practical for device simulation. In between the two extremes, it is possible to design intermediate models which preserve some essential features of both. At all levels of the band structure hierarchy of models, there are similar issues of numerical noise, related to the sampling of real and momentum space that the Monte Carlo method necessarily performs with a relatively small number of particles. We discuss here computationally efficient approaches based on the assignment of variable weights to the simulated particles, in conjunction with careful gatherscatter procedures to split particles of large weight and combine particles of small weight.

scholarly journals Reduced k-points based computationally efficient band structure approach for UTB device simulation

2021 ◽  
Author(s):  
Ravi Solanki ◽  
Nalin Vilochan Mishra ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Tight Binding ◽  
Computational Time ◽  
Thin Body ◽  
Computationally Efficient ◽  
Wide Range ◽  
Full Band ◽  
Consistent Solution ◽  
Full Band Structure

The accurate calculation of channel electrostatics parameters, such as charge density and potential, in ultra-thin body (UTB) devices requires self-consistent solution of the Poisson’s equation and the full band structure, which is channel material and thickness dependent. For cubic crystals like silicon, the semi-empirical sp3d5s* tight-binding (TB) model is preferred in device simulations, over the density functional theory, to obtain the full band structure because of being computationally less intensive and equally accurate. However, the computational time of the TB model scales non-linearly with the channel thickness and becomes cumbersome for silicon, beyond 5 nm, primarily because of the increasing size of the TB hamiltonian that needs to be solved over the entire k-space, in the irreducible Brillouin zone. In this work, we precisely identify those k-points corresponding to the energies close to the band minima, where the Fermi-Dirac probability significantly affects electrostatics parameters. This enables us to demonstrate a computationally efficient approach based on solving the hamiltonian only on those reduced number of k-points. The rigorous benchmarking of the channel electrostatics parameters obtained from this approach is performed with results from accurate full band structure simulations showing excellent agreement over a wide range of channel thicknesses, oxide thicknesses, device temperatures and different channel orientations. By showing that the approach presented in this work is computationally efficient, besides being accurate, regardless of the number of atomic layers, we demonstrate its applicability for simulating UTB devices.

scholarly journals Reduced k-points based computationally efficient band structure approach for UTB device simulation

2021 ◽  
Author(s):  
Ravi Solanki ◽  
Nalin Vilochan Mishra ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Tight Binding ◽  
Computational Time ◽  
Thin Body ◽  
Computationally Efficient ◽  
Wide Range ◽  
Full Band ◽  
Consistent Solution ◽  
Full Band Structure

The accurate calculation of channel electrostatics parameters, such as charge density and potential, in ultra-thin body (UTB) devices requires self-consistent solution of the Poisson’s equation and the full band structure, which is channel material and thickness dependent. For cubic crystals like silicon, the semi-empirical sp3d5s* tight-binding (TB) model is preferred in device simulations, over the density functional theory, to obtain the full band structure because of being computationally less intensive and equally accurate. However, the computational time of the TB model scales non-linearly with the channel thickness and becomes cumbersome for silicon, beyond 5 nm, primarily because of the increasing size of the TB hamiltonian that needs to be solved over the entire k-space, in the irreducible Brillouin zone. In this work, we precisely identify those k-points corresponding to the energies close to the band minima, where the Fermi-Dirac probability significantly affects electrostatics parameters. This enables us to demonstrate a computationally efficient approach based on solving the hamiltonian only on those reduced number of k-points. The rigorous benchmarking of the channel electrostatics parameters obtained from this approach is performed with results from accurate full band structure simulations showing excellent agreement over a wide range of channel thicknesses, oxide thicknesses, device temperatures and different channel orientations. By showing that the approach presented in this work is computationally efficient, besides being accurate, regardless of the number of atomic layers, we demonstrate its applicability for simulating UTB devices.

scholarly journals Monte Carlo Simulation of the Echo Signals from Low-Flying Targets for Airborne Radar

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Mingyuan Man ◽  
Zhenya Lei ◽  
Yongjun Xie ◽  
Botao Chen ◽  
Qing Wang
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Half Space ◽  
Ground Surface ◽  
Physical Optics ◽  
Airborne Radar ◽  
Average Value ◽  
The Monte Carlo Method ◽  
Multipath Effects ◽  
Actual Environment

A demonstrated hybrid method based on the combination of half-space physical optics method (PO), graphical-electromagnetic computing (GRECO), and Monte Carlo method on echo signals from low-flying targets based on actual environment for airborne radar is presented in this paper. The half-space physical optics method , combined with the graphical-electromagnetic computing (GRECO) method to eliminate the shadow regions quickly and rebuild the target automatically, is employed to calculate the radar cross section (RCS) of the conductive targets in half space fast and accurately. The direct echo is computed based on the radar equation. The reflected paths from sea or ground surface cause multipath effects. In order to accurately obtain the echo signals, the phase factors are modified for fluctuations in multipath, and the statistical average value of the echo signals is obtained using the Monte Carlo method. A typical simulation is performed, and the numerical results show the accuracy of the proposed method.

scholarly journals Monte Carlo Simulations of High Field Transport in Electroluminescent Devices

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 401-405
Author(s):  
Manfred Dür ◽  
Stephen M. Goodnick ◽  
Martin Reigrotzki ◽  
Ronald Redmer
Keyword(s):  
Band Structure ◽  
High Field ◽  
Light Emission ◽  
Essential Element ◽  
Impact Excitation ◽  
Field Energy ◽  
Pseudopotential Calculations ◽  
Full Band ◽  
Full Band Structure

High field transport in phosphor materials is an essential element of thin film electroluminescent device performance. Due to the high accelerating fields in these structures (1–3 MV/cm), a complete description of transport under high field conditions utilizing information on the full band structure of the material is critical to understand the light emission process due to impact excitation of luminescent impurities. Here we investigate the role of band structure for ZnS, GaN, and SrS based on empirical pseudopotential calculations to study its effect on the high field energy distribution of conduction band electrons.

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