多層含銻覆蓋層砷化銦量子點退火處理特性研究

本研究論文主要研究與探討砷化銦（InAs）量子點成長於砷化鎵（GaAs）基板上，覆蓋GaAs以及GaAsSb覆蓋層，製備多層垂直耦合量子點，並且研究成長後經高溫熱退火（Rapid Thermal Annealing）處理後，對於量子點品質改善與半導體光電特性之影響。研究中，我們利用穿透式電子顯微鏡（TEM）觀察多層垂直耦合量子點結構剖面，觀察到量子點使用GaAsSb覆蓋層後，量子點尺寸均勻性有所提昇，而在原子力顯微鏡（AFM）與掃描式電子顯微鏡（SEM）觀察量子點表面，發現使用GaAsSb覆蓋層後，量子點密度變高，並且沒有出現coalescence dots，顯示Sb元素改善量子點品質之效果。我們亦利用光激螢光光譜量測進行量子點之發光特性與載子生命期研究，結果發現，經退火處理後量子點之發光強度增強且光譜半高寬變窄，載子生命期延伸自4.7 ns到9.4 ns，顯見退火處理消除量子點中缺陷，改善量子點品質，然而，在過高的溫度進行熱退火處理後，則出現量子點結構潰散的現象，但也發現覆蓋GaAsSb覆蓋層之量子點能夠承受較高的退火溫度，維持量子點結構。此外，我們亦從變功率光激螢光光譜中發現熱退火處理後，高溫促使Sb元素聚集於量子點上方，致使覆蓋GaAsSb覆蓋層量子點能態結構轉變，由Type-I轉變成Type-II。將此延伸載子生命期以及量子點磊晶品質改善應用於量子點太陽電池中，將可望提昇電池轉換效率。

關鍵字

銻；量子點；快速熱退火；應力緩衝層；載子生命期

並列摘要

This study presents an improvement of the optical properties of a vertically aligned InAs/GaAs(Sb) quantum dot (QD) structure and the extension of the carrier lifetime therein by rapid thermal annealing (RTA). The atomic force microscope (AFM) and scanning electron microscope (SEM) images show that QD density and size uniformity improve with GaAsSb capping layer. Besides, the improvement of QD uniformity is ensured by the narrowed of photoluminescence (PL) spectra linewidth and transmission electron microscopy (TEM) images. Power-dependent PL (PDPL) and time resolved PL (TRPL) measurements on QD is performed to investigate the QD band structure and carrier lifetime. Those results indicate thermal stability that results from the suppression of In-Ga intermixing and preservation of the QD heterostructure in an annealed vertically aligned InAs/GaAsSb QD structure. PDPL and TRPL were utilized to demonstrate the extended carrier lifetime from 4.7 to 9.4 ns and elucidate the mechanisms of the antimony aggregation resulting in a band-alignment tailoring from straddling (Type-I) to staggered (Type-II) gap after the RTA process. These significant improvements in the carrier lifetime and optical properties of the columnar InAs/GaAsSb dot structure make the great potential in improving QD optoelectronic device applications.

並列關鍵字

Antimony ； Quantum dots ； Rapid Thermal Annealing ； Strain reducing layer ； carrier lifetime

參考文獻

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國際替代計量

多層含銻覆蓋層砷化銦量子點退火處理特性研究

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