以蒙地卡羅方法分析氮化銦鎵/氮化鎵發光二極體中載子的水平傳播及內部量子效率

Abstract

近年來，由於發光二極體在光照和顯示技術中扮演日漸重要的角色，如何改善其發光效率也越來越重要。目前為止，發光效率仍是限制發光二極體發展的主要因素之一。在本論文中，我們研究載子在氮化銦鎵/氮化鎵量子井中的行為，並且試著找出限制此結構的機制。我們應用了蒙地卡羅方法去分析自由載子在量子井中的水平傳播。首先，我們利用帕松、薛丁格和飄移擴散方程式去計算載子的輻射性復合率和輻射半生期。當載子進入量子井中，再利用蒙地卡羅的方法計算載子的水平遷移率並且估計出內部的最大量子效率。合金散射、錯位電荷散射、表面粗糙度散射以及電子-電子散射的效應都包含在我們的模型中。本論文包含了銦含量、表面粗糙度、載子密度、溫度以及錯位缺陷的研究討論。結果顯示，非輻射性復合的機制在較高的銦含量中扮演了重要的角色，原因是過長的輻射半生期，這限制了內部的量子效率。根據我們的結果顯示，減少量子侷限史塔克效應和錯位密度可以有效的改善內部量子效率。

Efficiency improvement of LED becomes more important when LED starts to play an important role in the applications of lighting and display technology. The efficiency is one of the key factors which impedes the progress of InGaN/GaN LEDs. In this thesis, we study the carrier dynamics in the InGaN/GaN quantum well and try to find what the mechanism limits the device performance. We have developed a Monte Carlo simulation program to study the lateral transport of free carriers in the InGaN/GaN quantum well. First, the radiative recombination rate and radiative lifetime of electrons are calculated by a self-consistent Poisson, Schrodinger and drift-diffusion solver. When carriers are injected into the quantum well, we calculated the lateral electron mobility and estimated the maximum internal quantum efficiency by the Monte Carlo method. The effects of alloying scattering, charged dislocation scattering, interface roughness scattering, and electron-electron scattering have been included in our model. The study of indium composition, interface roughness, carrier density, temperature, and dislocations are included in this thesis. The results show that the non-radiative recombination caused by defect trapping plays a dominating role for higher indium composition. This limits the internal quantum efficiency. Our results suggest that reducing QCSE and dislocation density are still the key factors to improve the internal quantum efficiency.