Implementation of Arithmetic Mean Method on Determination of Peak Junction Temperature of Semiconductor Device on Printed Circuit Board

High reliability users of microelectronic devices have been derating junction temperature and other critical stress parameters to improve device reliability and extend operating life. The junction temperature is what really matters for component functionality and reliability. This study presents a useful analysis on mathematical approach which can be implemented to predict thermal behavior in Integrated Circuit (IC). The problem could be modeled as heat conduction equation. In this study, numerical approaches based on implicit scheme and Arithmetic Mean (AM) iterative method will be applied to solve the governing heat conduction equation. From the numerical results obtained, it shows that AM method solves the governing heat conduction equation with minimum number of iterations and fastest computational time compared to the Gauss-Seidel (GS) method. It is in design phase when simulations and modeling are carried out to ensure high performance and reliability. The availability of thermal analysis tool for maximum temperature prediction would be of great value to designers of power device ICs

Accuracy of transfer matrix approaches for solving the effective mass Schr\"{o}dinger equation

The accuracy of different transfer matrix approaches, widely used to solve the stationary effective mass Schr\"{o}dinger equation for arbitrary one-dimensional potentials, is investigated analytically and numerically. Both the case of a constant and a position dependent effective mass are considered. Comparisons with a finite difference method are also performed. Based on analytical model potentials as well as self-consistent Schr\"{o}dinger-Poisson simulations of a heterostructure device, it is shown that a symmetrized transfer matrix approach yields a similar accuracy as the Airy function method at a significantly reduced numerical cost, moreover avoiding the numerical problems associated with Airy functions

Advanced modeling of nanoscale devices for analog applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Drift-diffusion models for innovative semiconductor devices and their numerical solution

We present charge transport models for novel semiconductor devices which may include ionic species as well as their thermodynamically consistent finite volume discretization

Nonlinear Coupled Effects in Nanomaterials

Materials at the nanoscale have different chemical, structural, and optoelectrical properties compared to their bulk counterparts. As a result, such materials, called nanomaterials, exhibit observable differences in certain physical phenomena. One such resulting phenomenon called the piezoelectric effect has played a crucial role in miniature self-powering electronic devices called nanogenerators which are fabricated by using nanostructures, such as nanowires, nanorods, and nanofilms. These devices are capable of harvesting electrical energy by inducing mechanical strain on the individual nanostructures. Electrical energy created in this manner does not have environmental limitations. In this thesis, important coupled effects, such as the nonlinear piezoelectric effect of a semiconducting wurtzite ZnO nanowire are studied by solving a time-dependent thermo-electromechanical model. For the examples considered here, the mathematical model consists of a system of fully-coupled nonlinear partial differential equations, and it is solved by using a variational formulation based on finite element representation. The numerical solution to this model is compared with the results obtained for the linear model of piezoelectric effect. The main focus has been given to the results from finite element analysis as a generalized model of the ZnO nanowire in order to understand its characteristics at an unperturbed state

Mobility Modeling of Gallium Nitride Nanowires

abstract: Semiconductor nanowires have the potential to emerge as the building blocks of next generation field-effect transistors, logic gates, solar cells and light emitting diodes. Use of Gallium Nitride (GaN) and other wide bandgap materials combines the advantages of III-nitrides along with the enhanced mobility offered by 2-dimensional confinement present in nanowires. The focus of this thesis is on developing a low field mobility model for a GaN nanowire using Ensemble Monte Carlo (EMC) techniques. A 2D Schrödinger-Poisson solver and a one-dimensional Monte Carlo solver is developed for an Aluminum Gallium Nitride/Gallium Nitride Heterostructure nanowire. A GaN/AlN/AlGaN heterostructure device is designed which creates 2-dimensional potential well for electrons. The nanowire is treated as a quasi-1D system in this work. A self-consistent 2D Schrödinger-Poisson solver is designed which determines the subband energies and the corresponding wavefunctions of the confined system. Three scattering mechanisms: acoustic phonon scattering, polar optical phonon scattering and piezoelectric scattering are considered to account for the electron phonon interactions in the system. Overlap integrals and 1D scattering rate expressions are derived for all the mechanisms listed. A generic one-dimensional Monte Carlo solver is also developed. Steady state results from the 1D Monte Carlo solver are extracted to determine the low field mobility of the GaN nanowires.Dissertation/ThesisMasters Thesis Electrical Engineering 201

Nonlinear Coupled Effects in Nanomaterials

Materials at the nanoscale have different chemical, structural, and optoelectrical properties compared to their bulk counterparts. As a result, such materials, called nanomaterials, exhibit observable differences in certain physical phenomena. One such resulting phenomenon called the piezoelectric effect has played a crucial role in miniature self-powering electronic devices called nanogenerators which are fabricated by using nanostructures, such as nanowires, nanorods, and nanofilms. These devices are capable of harvesting electrical energy by inducing mechanical strain on the individual nanostructures. Electrical energy created in this manner does not have environmental limitations. In this thesis, important coupled effects, such as the nonlinear piezoelectric effect of a semiconducting wurtzite ZnO nanowire are studied by solving a time-dependent thermo-electromechanical model. For the examples considered here, the mathematical model consists of a system of fully-coupled nonlinear partial differential equations, and it is solved by using a variational formulation based on finite element representation. The numerical solution to this model is compared with the results obtained for the linear model of piezoelectric effect. The main focus has been given to the results from finite element analysis as a generalized model of the ZnO nanowire in order to understand its characteristics at an unperturbed state

A Multiscale Thermo-Fluid Computational Model for a Two-Phase Cooling System

In this paper, we describe a mathematical model and a numerical simulation method for the condenser component of a novel two-phase thermosyphon cooling system for power electronics applications. The condenser consists of a set of roll-bonded vertically mounted fins among which air flows by either natural or forced convection. In order to deepen the understanding of the mechanisms that determine the performance of the condenser and to facilitate the further optimization of its industrial design, a multiscale approach is developed to reduce as much as possible the complexity of the simulation code while maintaining reasonable predictive accuracy. To this end, heat diffusion in the fins and its convective transport in air are modeled as 2D processes while the flow of the two-phase coolant within the fins is modeled as a 1D network of pipes. For the numerical solution of the resulting equations, a Dual Mixed-Finite Volume scheme with Exponential Fitting stabilization is used for 2D heat diffusion and convection while a Primal Mixed Finite Element discretization method with upwind stabilization is used for the 1D coolant flow. The mathematical model and the numerical method are validated through extensive simulations of realistic device structures which prove to be in excellent agreement with available experimental data