Modeling, Simulation And Analysis Of Semiconductor Devices: Research On High Power LED Devices And Semiconductor Piezoresistive Devices  Posted on:20151027  Degree:Doctor  Type:Dissertation  Country:China  Candidate:W F Dai  Full Text:PDF  GTID:1108330464959239  Subject:Materials Physics and Chemistry  Abstract/Summary:  PDF Full Text Request  This thesis of my work is mainly about the simulation and analysis of semiconductor devices which contains two part:(1) The first is the solution of techniques of the modeling, simulation and thermal analysis of highpower lightemitting diodes (LED); the second part is composed by modeling study and simulation of organic semiconductor piezoresistance devices.In the first part:Surrounding structuremodelheat dissipation problems in highpower LED system, we established systematical method of device analysis for highpower LEDs and built a related tool of parameterized finiteelement analysis.Our study contains:(1) Theoretical analysis on heat dissipation of highpower LED and primary study on factors of heat transfer in LED system; (2) based on material analysis method (experimental), we investigate several factors impacting LED’s heat dissipation and establish a solution for structure analysis and parameter extraction from macroscope to microscope; (3) for thermal analysis of highpower LED device, we customized and made second development on the related opensource FEM software and designed a parameterization thermal simulation package with other opensource tools; (4) we analyze a real commercial highpower LED device by using forementioned method and tools. The total study are listed below:1. Theoretical analysis of highpower LED’s thermal problems. After investigation of paper references, based on the elementary knowledge of highpower LED’s package technology, we made a general theoretical analysis for the heat dissipation of LED device. Based on the theory of thermal resistance network, we analyze the impact on the device heat dissipation of those interfacial factors. The analysis shows that the main joule conduit is constructed of several interfaces which affect the total heat conduction much. Once interfacial defects block the main joule conduit, the total thermal resistance, tending to the part with higher thermal resistance, will grow higher.2. Solution of structure analysis and parameter extraction. By applying microanalysis method, we established a systematical solution for device analysis from nondestructive analysis to destructive analysis. Based on this solution, we analyze a series of highpower LED devices and extract related parameters and material information, then we compare the similarities and differences of their processes. As result, we recognize that bonding interface in LED device highly impact the total thermal resistance. We have observed many defects existed in the AuSn soldering interface which may cause increasing of total thermal resis tance. As this experimental results, we extract related parameter for FEM simulation.3. Development of Parameterized FEM simulation solution. By studying and comparing the opensource FEM tools and the commercial counterpart, we choose and expand the opensource software to do parameterized FEM analysis. We did second development for GMSH to simplify establishing parameterized models of the highpower LED device. Then we customize GetDP for adapting that parameterized model and processing transient thermal analysis. Combining other opensource like Python language and GNU Make, we designed a parameterization program package for FEM simulation with file interface and controlled the solving flow. We have made a whole package as a parameterization FEM solution for highpower LED’s thermal analysis. The numerical problems (stability, accuracy and convergence) and impact of physical parameters on the iteration process are varified in this study by calculating simplified models. The result indicates that the optimized iteration method is more efficient with numerical stability, accuracy and convergence.4. Study of parameterization FEM simulation for a highpower LED device. Based on the theory of the first part, the experiments of the second part and the tools of the third part, we study the thermal problem of a flipchip highpower LED with complicated structure by parameterization FEM method. The conclusions are:(1) The geometric size of gold bump has limited effect on the total heat dissipation; (2) The defects in AuSn soldering interface may cause rising of the junction temperature at higher input power (about 4w); (3) We study impact of the exterior heat sink fin’s number on the total heat dissipation under two different device/exterior sink interface:one is metal solder bonding, the other is silicone grease bonding, in result, the more fins (48) will cause junction temperature reducing about 10 degrees to less fins (12).The second part:we study the organic semiconductors that used in piezoresistance devices.The experimental data (nanoindentation instrument) shows a currentsaturated effect on the piezoresistance film device. We extend the MillerAbrahams model on this case and build currentstrain(stress) curve. The electrical and mechanic factors are both concerned in our study. The work contains:1. Building physical model. Based on MillerAbrahams model and reasonable assumption of interfacial carriertransfer behaviors, we get a current formula containing the saturation effect. The asymptotic behavior of the formula suggests two different carrier transfer mechanics. When the pressure goes up, the interfacial charge injection is restricted, which affect the carrier distribution beside and causes the current growth and finally the current saturation.2. Characterization of the mechanical properties of the device film. Introduce mechanic test of the device film and convert the currentstress data to currentstrain data, from which we the nonlinear mechanic properties of film is only a part of reasons for the current saturation.3. Numerical simulation. We use Monte Carlo method to simulate the carrier transfer behavior in the film and get the currentstrain curve. Under a higher exvoltage, energy disorder will not impact the linear relation between strain and log current.4. Fitting. Using forementioned equation, we fit the experimental data and found that the theory matches well.  Keywords/Search Tags:  Highpower LED, Numerical Simulation, FiniteElement Method, Interface, thermal analysis, parameterization, opensource tools, organic semiconductor, piezoresistance device  PDF Full Text Request  Related items 
 
