改變M面 ZnO/MgZnO 量子井之井寬並研究其光學特性

Abstract

本論文主要研究非極性ZnO/MgZnO量子井結構的成長及透過改變井寬探討其光學特性。使用脈衝雷射濺鍍法成長量子井結構於長有兩階段成長的Mg0.9Zn0.1O緩衝層的M面藍寶石基板上，我們得到具有更佳的晶相與表面平整度的量子井結構。與我們之前使用Mg0.8Zn0.2O作為障壁層之量子井比較，製程上使用Mg0.9Zn0.1O作為障壁層和不同溫度成長障壁層與量子井，使得量子井發光波形變得更窄。我們也發現當縮小量子井寬度時，會造成近能隙邊緣發光與另一個受基面堆疊缺陷束縛的放射光產生藍移的現象。另外，我們從分析激子與聲子的交互作用以及激子的結合能，了解量子侷限效應在樣品中扮演重要的影響。過程中，我們也使用了不同的分析方式去證明在我們製作的樣品中並沒有量子侷限史塔克效應的作用。論文中也對非極性多重量子井的光學特性進行光學非均向性的探討。最後，我們透過觀察量子井寬為11奈米的樣品之光學特性，發現其許多光學特性並不符合趨勢，並從中探討(101 ̅3)結構在多重量子井的影響。

We report in this thesis experimental study on optical properties of nonpolar ZnO/MgZnO multiple quantum wells (MQWs) on m-sapphire with different well widths grown by pulsed laser deposition. The nonpolar ZnO/Mg0.1Zn0.9O was fabricated on Mg0.1Zn0.9O buffer by two-step growth, which effectively reduces the extra domain and surface roughness. Use 10% MZO as barrier and two temperatures to fabrication well and barrier, we can obtain narrower FWHM of well emission. On investigating the optical properties of different well-width MQWs by photoluminescence, we found the emission of near-band edge and basal-plane stacking faults are blue-shifted as decreasing the well width. The result of exciton and LO-phonon coupling and exciton binding energy for each sample reveal that the quantum confinement effect plays a dominant role. Additionally, we use several analyses to prove that there is absence of the quantum confined Stark effect in our samples. We also discuss the optical anisotropy properties of our nonpolar MQWs. Finally, through observing many optical behaviors for the thickest well width sample which does not follow the same trend as the others, we understand the influence of extra (101 ̅3) domain in well width 11 nm MQWs.