管傑雄臺灣大學：電子工程學研究所陳冠廷Chen, Kuan-TingKuan-TingChen2007-11-272018-07-102007-11-272018-07-102004http://ntur.lib.ntu.edu.tw//handle/246246/57410矽鍺光電元件具有與矽積體化電路整合的優點，加上量子異質接面結構的長晶技術進步，因此近年來矽鍺異質接面的光電元件被廣為研究。而本論文中提出室溫操作且發光波段在1.3-1.4微米之多週期矽/矽鍺超晶格發光二極體。 在本篇論文中我們利用超高真空化學氣相沈積成長一系列週期數不同的矽/矽鍺超晶格結構，並探討週期數對於矽/矽鍺超晶格電激發光特性之影響，特別是在發光頻譜的變化。根據實驗結果，我們發現隨著週期數增加其發光效率也跟著增加；此外由於空乏區包含所有P型低摻雜區域，所以室溫時少數載子(電子)易穿越作用區而擴散至P型高摻雜區域(覆遞h)，造成Si波段放光；不過在低溫時由於量子井侷限效應增強，且多週期數提供更強的輻射與非輻射復合，因此只有超晶格結構的波段放光。 另一部份我們探討了矽/矽鍺超晶格與鍺量子點的發光強度比較，雖然鍺量子點提供三維的侷限效應並且其缺陷密度較小，但由於分佈密度小，造成發光區域小於矽/矽鍺超晶格，因此鍺量子點的發光強度將小於矽/矽鍺超晶格。不過若能增加鍺量子點成長密度，將可加強其發光強度。The advantage of the optoelectronic component of silicon germanium is fully compatible with the Si-based microelectronic chips. In addition, the progress of the growth techniques for quantum heterojunction structure is in advanced. So the heterojunction structure of silicon germanium is studied far and wide in recent years. In this thesis, the light-emitting diodes (LEDs) with multi-periods of Si/SiGe superlattice operating at room temperature for 1.3-1.4μm emission wavelength are reported. We design a series of different period number Si/SiGe superlattice structures that is grown by UHV/CVD system in this thesis. Then we analyze the influences of period number of Si/SiGe superlattice on electroluminescence characteristics, especially the electroluminescence (EL) spectra. According to experimental result, the emission intensity from SL is enhanced with increasing period number. In addition, because the depletion region covers all the P-type lightly doped region, so the minority carriers (electrons) will go through the active region and diffuse into P-type heavily doped region (capping layer). Then, electrons will recombine with holes and emit the light of Si wavelength at room temperature. However, at low temperature, the more layer superlattice provides the enough quantum wells to capture injection holes and its stronger confinement causes the higher radiative and nonradiative recombination rate. So that will emit the light of superlattice structure wavelength only. At another part, we compare the luminescence intensity between the Si/SiGe superlattice and Ge quantum dots. Although the quantum dot offers 3D-confinement and its trap density is smaller than superlattice, but its distribution density is small and causes the luminescense area is smaller than Si/SiGe superlattice. Therefore, the luminescence intensity of Ge quantum dots is weaker than Si/SiGe superlattice. But if we can increase the distribution density of Ge quantum dots, its luminescence intensity can be strengthen.Chapter 1 Introduction 1 References 7 Chapter 2 Background of Si/SiGe Superlattice and Light Emission 9 2.1 Si/SiGe Superlattice 9 2.1.1 Si1-xGex Strained Layer 9 2.1.2 Si/SiGe Mutiple Quantum Well and Superlattice Structure 13 2.1.3 Bandgap and Band alignment of Si/SiGe Heterostructure 15 2.2 The Essential Principle of Light-Emitting Diode 19 2.2.1 Eletroluminescence 19 2.2.2 Light Emitting Diode 19 References 21 Chapter 3 Experimental Procedures of Fabricating LED Devices and Measurement Instrument Setup 22 3.1 Fabrication Processes 22 3.1.1 Sample Cleaning 24 3.1.2 First Photolithography for the Pattern of Mesa 25 3.1.3 Wet Etching for the Mesa 27 3.1.4 Metal Evaporation for Backside Contact 30 3.1.5 Second Photolithography for the Pattern of Transparent Contact 30 3.1.6 Metal Evaporation for Transparent Contact and Lift-off 31 3.1.7 Third Photolithography for the Pattern of Top Contact 32 3.1.8 Metal Evaporation for Top Contact and Lift-off 32 3.1.9 Annealing for Ohmic Contact 32 3.1.10 Wire Bonding 33 3.2 Instruments Setup for Measurements 35 3.2.1 Current-Voltage (I-V) 35 3.2.2 Luminescence Intensity (L-I curves) 35 3.2.3 Electroluminescence (EL) Spectrum 36 References 39 Chapter 4 Light Emission Diodes Made by Si/SiGe Superlattice with Different Period Number 40 4.1 Sample Preparation 40 4.2 Current-Voltage (I-V) Characteristics 45 4.3 Current-dependent Electroluminescence (EL) Spectra 46 4.3.1 Room-Temperature (300K) EL Spectra 46 4.3.2 Low-Temperature (30K) EL Spectra 47 4.4 L-I Characteristics 50 4.5 Temperature-dependence of Integral Intensity 54 4.6 Summary 58 References 59 Chapter 5 Discussion of Si/SiGe Superlattice Electroluminescence Characteristics and Comparison with Ge Quantum Dots 60 5.1 Possible Mechanism for EL Characteristics of Si/SiGe Superlattice 60 5.2 The injection holes captured in the wells 67 5.3 LI Comparison between Si/SiGe SL and Ge QDs 71 References 76 Chapter 6 Conclusion and Future Work 772083376 bytesapplication/pdfen-US矽鍺超晶格矽電激發光SiGeSiElectroluminescenceSuperlatticethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/57410/1/ntu-93-R91943029-1.pdf