氧化鋅和氧化鎂鋅多層量子井成長在氧化釔緩衝層的矽基板上之光學與結構特性探討

Abstract

本論文於最被廣泛應用的半導體材料矽基板上製作高品質的氧化鋅/氧化鎂鋅多重量子井並研究其結構與物理特性。我們在氧化鋅緩衝層(buffer layer)與矽基板之間插入數奈米厚的氧化釔的磊晶層大幅改善其上的氧化鋅/氧化鎂鋅多重量子井的結構完美程度。在氧化鋅/氧化鎂鋅多重量子井結構中以氧化鎂鋅做為位能屏障層的材料，經由晶格常數與陰極激發光譜分析結果推估鎂的摻雜濃度約高於33%，且氧化鎂鋅沒有形成相分離的結構。X光晶體斷柱圖譜中觀察到高階衛星峰和高解析穿透式電子顯微鏡影像中呈規則排列的位能井與屏障層結構證實多重量子井具高品質的磊晶結構。我們詳細研究位能井的厚度變化對氧化鋅/氧化鎂鋅多重量子井的近能隙邊緣發光特性的影響。隨著量子井寬度變小光激螢光的發光峰位置呈現明顯的藍移現象，反映量子侷限效應的產生。在低溫光激螢光譜改變雷激發光率的實驗中，我們發現當量子井寬度小於氧化鋅的波爾半徑時(~3 nm)，內建電場的影響可以忽略不計。此外，藉由不同溫度下光激螢光光譜的變化，我們探討光激螢光中所產生的載子的侷限、弛豫與複合等行為。我們的研究結果顯示結合氧化鋅/氧化鎂鋅多重量子井與矽基板於紫外光波段的光電元件應用上非常具有潛力。

This thesis reports the growth and physical properties of ten-period ZnO/MgxZn1-xO multiple quantum wells (MQWs) prepared on the most widely used semiconductor material, Si. The introduction of a nm-thick Y2O3 transition layer between Si (111) substrate and a ZnO buffer layer significantly improves the structural perfection of the MQWs grown on top of it. Single phase MgxZn1-xO with Mg contents x approximately higher than 0.33, as determined from its lattice constants and cathodoluminescence emitted peak position, was adopted as the barrier material. The high structural quality of the ZnO/MgxZn1-xO MQWs is evidenced by the appearance of pronounced high order satellite peaks in X-ray crystal truncation rods; high resolution cross-sectional TEM images also confirmed the regularly arranged well and barrier layers. We studied the dependence of the near-band edge (NBE) emission transition in ZnO/MgxZn1-xO MQWs on well layer thickness in details. The dominated PL peak of the MQWs shows a significant blue shift with decreasing well width, which is consistent with the quantum confinement effect. From the power-dependent PL spectra conducted at 10k, we observed that built-in electric field effect in MQWs can be negligible when the well width is less than ZnO excition Bohr radius (~3 nm). Moreover, the temperature dependence of PL spectra is investigated to reveal the localization, relaxation and recombination mechanisms of the photo-generated carriers. Our results indicate that ZnO/MgxZn1-xO MQWs integrated on Si have great potential in UV optoelectronic device applications.