Light Emission from Metal-Oxide-Semiconductor Tunneling Diodes and the Strain Effect

本論文中，我們利用金氧半（MOS）穿隧二極體中穿隧閘極電流與累積的多數載子結合發光的特性來製作發光二極體。由於鍺融點的關係我們以液相沈積法代替傳統的熱成長法來成長氧化層，且由於液相沈積法成長的氧化層有較多的缺陷所以有較高的效率。我們建構了一種機制來施加外在的伸展應力。在施加外加的伸展應力之下，我們觀察到矽的能隙縮減還有光強度的增加。這是因為外加伸展應力使得矽的價電帶往上移動以及導電帶向下移動造成。價電帶的向上移動會使得氧化層以及矽的接面的電洞濃度增加。本論文中提出矽鍺量子點以及矽鍺異質接面金氧半發光二極體，用來提升矽基金氧半發光二極體的發光波長至1.5微米(一個光纖通訊中重要的波段)以及2微米。1.5微米波長的產生來自於侷限在矽鍺量子點中的電子與電洞的結合，而2微米波長的產生是來自於侷限在鍺價電帶量子井的電洞以及在矽覆蓋層的電子結合。我們也從電激發光（EL）頻譜觀察到這兩種金氧半發光二極體受到外加伸展應力產生的效應。此外，我們也觀察到二十層矽鍺量子點樣本的發光頂點波長的能量比五層矽鍺量子點樣本要高出千分之十六電子伏特，這是由於二十層矽鍺量子點在成長過程中所受應力鬆弛較多的緣故。In this thesis, the metal-oxide-semiconductor (MOS) tunneling diodes were utilized as light emitting diodes based on that the tunneling gate current recombines with accumulated majority carriers and results in radiative luminescence. We used liquid phase deposition (LPD) method in stead of traditional thermal method to deposit oxide films, and the LPD has higher efficiency due to more defects in it. We brought up a mechanical set up to apply external tensile strain. The reduction of Si band gap and the enhancement of light intensity under external tensile strain are observed. The upshift of valence band edge and the downshift of conduction band edge under tensile strain are responsible for that. The upshift of valence band edge under mechanical strain increases the majority hole concentration at the oxide/Si interface. The SiGe QD and Si/Ge heterojunction MOS LED were reported in this thesis to extend the emission wavelength of Si-based MOS LED to ~1.5 ( an important wavelength for fiber-communication) and ~2 . The origin of the ~1.5 emission is due to the radiative recombination between the electrons and holes confined in the SiGe QD and the ~2 light emission is due to the recombination of holes on the valence bandedge of the Ge quantum well and the electrons on the conduction bandedge of the Si cap. The tensile strain effect of these two kinds of MOS LEDs was also investigated from EL spectra data. In addition, the emission peak of 20-layer SiGe QDs sample is observed 16 meV higher than that of 5-layer SiGe QDs sample due to more relaxation during growth.Chapter1……………………………………………………… 1 Introduction..................................................................................1 1.1Motivation...........................................................................................1 1.2Thesis Organization.......................................................................3 Chapter 2..........................................................................................5 Electroluminescence from metal/oxide/ strained-Si tunneling diodes..........................................................................5 2.1 Introduction.........................................................................................5 2.2 Growth of LPD Oxide and Basic Theory for Light Emission of NMOS Tunneling Diodes.................................................................7 2.2.1 LPD process flow..................................................................7 2.2.2 Basic Theory for Light Emission from MOS Tunneling Diodes..............................................................................8 2.3 Experimental setup.......................................................................11 2.3.1 Experimental Setup for Electroluminescence measurement…………………………………………...11 2.3.2 micro-Raman Experiment Setup.....................................12 2.4 Experimental Results and Discussion..........................................13 2.5 Conclusion....................................................................................20 Chapter 3………………………………..……………………23 Strained Si/Ge heterojunction metal- oxide- semiconductor tunneling diodes...........................................23 3.1 Introduction..................................................................................23 3.2 Device Fabrication…………………………………………....... 25 3.3 Strain Analysis from micro-Raman experiment……………….. 30 3.4 Light from Si/Ge Heterojunction LED………………………….33 3.4.1 Experimental Setup.............................................................33 3.4.2 Experimental Results and Discussion…………………35 3.4.3 The Second Order (Alias) Checking…………………...39 3.4.4 External Strain Effect…………………………………..41 3.5 Conclusion………………………………………………………44 Chapter 4……………………………………………………..48 Electroluminmescence from the SiGe quantum dot metal-oxide-semiconductor tunneling diodes………...48 4.1 Introduction……………………………………………………..48 4.2 Device Fabrication………………………………………………49 4.3 The Ge Composition of SiGe QDs and The Raman Analysis…..53 4.4 Light from SiGe QDs Tunneling Diodes………………………..58 4.5 Conclusion………………………………………………………64 Chapter 5……………………………………………………..69 Summary and Future Work……………………………..69 5.1 Summary………………………………………………………69 5.2 Future Work……………………………………………………7