以金屬有機化學氣相沉積法成長砷化鎵薄膜於矽基板之研究

The Study of GaAs Films Grown on Si Substrate by MOCVD

連建惟(Jian-Wei Lian)

指導教授 ： 温武義

中原大學/電機資訊學院/電子工程研究所/碩士(2020年)

https://doi.org/10.6840/cycu202000444

摘要

本論文利用金屬有機化學氣相沉積法於矽基板上成長砷化鎵薄膜，眾知砷化鎵與矽兩者之間存在著4%的晶格不匹配，所以在磊晶時會產生許多的缺陷，因此我們結合兩階段成長法及熱循環退火技術(TCA)來成長砷化鎵薄膜，以降低其缺陷，並藉由改變TCA的次數，對薄膜品質進行研究及分析。
由實驗結果發現，隨著TCA次數的增加(0次、1次、2次、3次、4次)，薄膜品質會隨之提高，X光繞射儀搖擺曲線量測到的半高寬由267 arcsec縮小至100 arcsec，但是表面也因為多次退火的關係，變得越來越粗糙，由此得知， TCA次數與結晶品質呈正相關，與表面粗糙度呈負相關。
最後，我們以經過4次TCA的GaAs/Si異質磊晶結構與GaAs/GaAs同質磊晶結構各自製做成單接面太陽能電池，並進行電性的量測與比較，結果顯示利用異質磊晶結構所研製元件之開路電壓及填充因子約為利用同質磊晶結構所研製元件的79%~91%，代表GaAs/Si異質磊晶薄膜間仍有不少缺陷存在，影響內部載子垂直方向的移動，進而導致光轉換效率降低。

關鍵字

兩階段成長法 ； 熱循環退火 ； 砷化鎵薄膜

並列摘要

In this paper, GaAs films were grown on Si substrate by metal-organic chemical vapor deposition. As known, the preparation of GaAs-on-Si heteroepitaxial structure is very difficult due to quite different lattice constant and thermal expansion coefficient between these two semiconductor materials.
Therefore, direct epitaxial growth of GaAs on Si is accompanied by the formation of a large number of defects.
A technique for the growth of GaAs films on Si which combined a two-step growth method with thermal cycle annealing (TCA) was developed to reduce the defects. The quality and roughness of GaAs films on Si were investigated by X-ray diffraction (XRD) and atomic force microscope (AFM).
It was found that the full width at half maximum value of XRD rocking curve for GaAs deposited films was decreased from 267 arcsec to 100 arcsec as the number of TCA heat treatment increased from zero to four. However, the AFM analyses demonstrated the surface roughness was increased from 11.6 nm to 40.2 nm. In summary, the more the number of times of TCA performed the higher quality of GaAs film would be achieved, however, the film surface morphology would also become rougher correspondingly.
Finally, we used the GaAs/Si heteroepitaxial structure that have undergone four TCAs and GaAs/GaAs homoepitaxial structure to make single-junction solar cells and conducted electrical measurements and comparisons. The results show that both the open circuit voltage and fill factor of the device developed by the hetero-epitaxial structure are about 79%~91% of the device developed by the homo-epitaxial one, which means that there are still many defects in the GaAs/Si heteroepitaxial film, which affect the light conversion efficiency of the solar cell produced.

並列關鍵字

two-step growth method ； thermal cycle annealing ； GaAs films

參考文獻

參考文獻

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