Fabrication and Characterization of Electroluminescent Metal-Oxide-Semiconductor Silicon Tunneling Diodes

本論文著重在金氧矽發光二極體之製作與分析，特別是使用二氧化矽奈米粒子作為氧化層的裝置。使用二氧化矽奈米粒子造成載子侷限，因而促進了發光效率。在金氧矽發光二極體中，放光-電流特性以及放光的頻率反應時間會隨注入電流而改變。根據這些特性，我們推導了一個載子動力模型來統一解釋電流-電壓特性、放光-電流特性、以及小信號放光頻率反應隨電流改變的關係。由此理論推斷出此裝置的放光效率為數十個百分比。我們在使用二氧化矽奈米粒子的金氧矽發光二極體中加入了矽奈米結構，來促進載子侷限，可增加百分之三十的發光效率。我們從載子動力模型發展出金氧矽發光二極體中的光增益模型，因而推導矽半導體中居量反轉的條件以及光增益係數。我們推導了金氧矽發光二極體中操作在不同的電壓與電流下的光增益係數，其數值在光子能量為矽能隙時約為1cm-1。在使用金氧矽發光二極體做為發光層的電激發矽波導中，要使受激放光發生，其 散射損失必須小於1cm-1。此條件等同於要求此波導的側璧之均方根粗糙度須小於1nm。我們發展了雷射重組的技術，能夠降低均方根粗糙度至0.239nm。The fabrication and characterization of the electroluminescent metal-oxide-semiconductor tunneling diodes (MOS-TD) based on silicon are presented in this dissertation. A special case of MOS-TDs, which uses SiO2 nanoparticles as the oxide layer, is studied. The use of SiO2 nanoparticles results in carrier confinement and enhances light emission. In MOSTDs, the light-current relation, and the frequency response lifetime are found to vary with the injection current density. A carrier dynamic model based on characteristics of MOS-TDs is developed to explain the current-voltage relation, the light-current relation, and the small signal frequency response. The theoretical internal efficiency is estimated to be several tens of percents. A nanostructured MOS-TDs using SiO2 nanoparticles is fabricated to improve the carrier confinement and shows a 30% more light emission efficiency. An optical gain model in MOS-TDs is developed based on the carrier dynamic model. The criterion of population inversion and the optical gain coefficients in Si are derived. The optical gain coefficients are calculated at different voltages and currents in MOS-TDs, whose magnitudes are about 1 cm-1 at the silicon bandgap energy. For stimulated emission to occur in an electrically pumped Si waveguide, which uses the MOS-TD as the active region, the scattering loss has to be less than 1 cm-1. This corresponds to a root-mean-square (RMS) roughness of less than 1 nm at the waveguide sidewalls. A laser reformation technique capable of reducing the RMS roughness to 0.239nm is developed.Table of Contents Chapter 1 Introduction 14 1-1 Backgrounds 14 1-2 Outlines 16 Chapter 2 Fabrication of electroluminescent metal-oxide-semiconductor silicon tunneling diodes using silicon dioxide nanoparticles 22 2-1 Introduction 22 2-2 Fabrication of an EL MOS-TD using SiO2 nanoparticles 24 2-3 Operation of EL MOS-TDs using SiO2 nanoparticles 26 2-4 Influence of fabrication processes on EQE 31 2-5 Summary 32 Chapter 3 Rigorous carrier dynamic model of electroluminescent MOS-TDs 36 3-1 Introduction 36 3-2 Modeling of current densities 39 3-3 Light emission efficiency 57 3-4 Small signal light-current response 59 3-5 Summary 51 Chapter 4 Fabrication of Si nanorods in MOS-TDs by reactive ion etch 75 4-1 Introduction 75 4-2 Anisotropic control 77 4-3 Etch mask preparation 82 4-4 Silicon nanorods 84 4-5 Etch damage 87 4-6 Performance of Si nanostructured MOS-TDs 91 4-7 Summary 92 Chapter 5 Optical gain model in Si MOS-TDs 98 5-1 Introduction 98 5-2 Indirect optical interactions in Si 100 5-3 Optical gain coefficients 109 5-4 Summary 117 Chapter 6 Smooth Si waveguides by laser reformation 121 6-1 Introduction 121 6-2 The relation of roughness and scattering loss 124 6-3 Fabrication processes of the smooth waveguides 127 6-4 Preparation of the excimer laser 129 6-5 The crystal quality after laser reformation 130 6-6 Shape deformation 132 6-7 Roughness analysis 135 6-8 Smoothed Si waveguides 140 6-9 Summary 143 Chapter 7 Conclusion 14