Catálogo de publicaciones - libros

In order to investigate the technological potential ascribed to semiconductor nanowires, it is paramount to include quantum effects into the models used to simulate carrier trans-port as well as optical and excitonic features of various nanowire layouts.

In particular, one needs to determine the energy eigenvalues and eigenfunctions of the charge carriers in terms of material parameters and tunable parameters, such as the external voltages and the wire radius. As the latter may be running from a few nanometers up to a few tens of nanometers, the number of occupied subbands may substantially in-crease. Consequently, a flexible Poisson-Schrödinger solver needs to be invoked to minimize the computational burden, especially when it is to be integrated into another Simulation program.

Atomistic simulations of transport properties of an ultra-scaled Silicon nanowire (SiNW) field-effect transistor (FETs) in a Gate-All-Around configuration are reported. The calculations have been obtained using a semi-empirical tight-binding representation of the System Hamiltonian based on first-principles density functional theory (DFT). An efficient non-equilibrium Green’s functions (NEGF) scheme has been implemented in order to compute self-consistently the charge density and the electrostatic potential in the SiNW Channel.

An alytical expression for the dependence of the nonparabolicity parameter on shear stress is presented. At 3 GPa the nonparabolicity parameter is shown to increase by a factor of 1.7. Stress dependence of the nonparabolicity parameter is verified by comparing the density-of-states obtained analytically and from the empirical pseudopotential method, and good agreement is found. Increase in the nonparabolicity parameter increases the after-scattering density-of-states and hence the scattering rates, which results in a 25% suppression of the mobility enhancement due to effective mass decrease in a 3 nm thin body FET at 3 GPa [110] stress.

It is announced that the Maxwell equations can be solved on unstructured grids using finite integration methods. Numerical experiments show that next to the finite-volume method, a discretization technique can be defined based on ‘finite-surface’ integration.

This paper describes a numerical method for a time-dependent quantum drift-diffusion model with emphasis on adaptive time discretization. The adaptive time step algorithm is proposed by introducing the derivative of the free energy of the system. The algorithm is evaluated for carrier transport simulations in n-n-n structures. The new algorithm significantly reduces the total number of time step required to reach the stationary state.

Device simulation needs are growing more diverse and it is difficult for traditional simulators to satisfy them while maintaining usability, maintainability, speed, and robustness. The Modular Device Simulator (MDS) is a completely new simulator framework that addresses this problem by providing simulation building blocks within a dynamic, runtime-configurable framework driven by a scriptable input parser. This flexible framework allows MDS to be applied to a wide range of problems that traditionally would have been handled by many independent codes. MDS has been applied to the 45 nm node and beyond, including advanced applications such as Schrödinger/drift-diffusion and non-equilibrium Green’s function (NEGF).

In this work, we included Poole-Frenkel (P-F) detrapping mechanism to our simulator to calculate programming/erasing characteristics of charge trapping memory, and comprehensively analyze the impacts of temperature, trap depth and parameters of P-F model on program window and erasing speed. Our results reveal that Poole-Frenkel effect could accelerate the erasing operation, but it also could reduce the program window and cause the electric characteristics sensitive to temperature.

The small dimensions of the on-chip interconnect structures provide the interesting opportunity of using the optimized model of dominant magnetic field even at very high operating frequencies for inductance and resistance extraction. The parameters are obtained from the field energy calculated from the magnetic field distribution in the simulation domain. Vector and scalar shape functions are used for finite element equation system assembling. Series of simulations for an on-chip spiral inductor at frequencies between 1 MHz and 100 GHz are performed to extract the parameters and to visualize the field distributions in the simulation area.

We report on several ultrafast electron transport phenomena occurring in wurtzite InN which are considered as the physical mechanisms responsible for the THz electric field radiation. We apply the ensemble Monte Carlo (EMC) method to simulate the streaming transport caused by (a) optical phonon emission and (b) impact ionization. Under specific conditions, in both streaming regimes the electron drift velocity reveals the sub-picosecond oscillations which are an indication of “readiness” of the semiconductor system to radiate an electric field in the THz range. We also investigate the electric field emission from InN and InAs surfaces induced by femtosecond laser excitation.

In this paper, we numerically study the discrete-dopant-induced characteristic fluctuations in 16nm silicon-on-insulator (SOI) FinFETs. For devices under different temperature condition, discrete dopants are statistically generated and positioned into the three-dimensional channel region to examine associated carrier transportation characteristics, concurrently capturing “dopant concentration variation” and “dopant position fluctuation”. Electrical characteristics’ fluctuations are growing worse when the substrate temperature increases, the standard deviation of threshold voltage increases 1.75 times when substrate temperature increases from 300K to 400K for example. This “atomistic” device simulation technique is computationally cost-effective and provides us an insight into the problem of discrete-dopant-induced fluctuation and the relation between the fluctuation and thermal effect.