Electronic and Thermal Analysis of High Power InGaN/GaN light Emitting Diodes with Finite Elementethods
Date Issued
2009
Date
2009
Author(s)
Li, Chi-Kang
Abstract
InGaN/GaN LEDs offer important lighting devices for human livings. These devices have high efficiency and lifetimes at low injection power but so far show degradation under high injection conditions. Current spreading and heat dissipation are key reasons for degradation under high power operation. In this thesis, we have developed a three-dimensional (3-D) finite element method (FEM) to examinehe heat generation and dissipation and a two-dimensional (2D) Finite element Poisson and drift-diffusion solver for the analysis of current spreading. As we know, the junction temperature plays an important role to the performance of the LED, and it will influence the opticalerformance. Therefore, the discussion of different structures for LED chips and packages will be considered in this thesis. We have examined how current flow can be altered by a careful design of the LEDs. We can find that higher thermal conductivity of the materials used in thehip or package can lead to a better heat dissipation especially in it near the heat source region. Also, when the number of layers between the chip and bottom heat sink are becoming less, the effect of heat dissipation can be promoted. Results for a conventional LED and a LED with ion-implantation to improve current flow are also presented. Our simulations show that with better design of the current spreading can improve the device operation.
Subjects
InGaN
GaN
high power LED
junction temperature
Poisson equation
drift-diffusion
current spreading
finite element method
Type
thesis
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