成長磷化銦鎵材料於砷化鎵及鍺/矽基板上對三五族太陽能電池應用之研究

Abstract

對低成本高效率的三五族太陽能電池而言，使用矽作為替代性基板來取代昂貴及傳統的鍺基板將會成為未來重要的趨勢。於磷化銦鎵/砷化鎵/鍺/矽異質結構的磊晶成長過程中，磷化銦鎵/砷化鎵磊晶層的異質接面對於整體結構佔有重要的因素。高品質的磷化銦鎵磊晶層於砷化鎵/鍺/矽基板上將更一步提升三五族太陽電池於矽基板上的元件效能。在本論文中，我們首先使用有機金屬化學氣相沉積系統成長磷化銦鎵於砷化鎵基板上，這將有助於得到磷化銦鎵/砷化鎵磊晶成長的基本參數與材料特性等資料，接著轉移到砷化鎵/鍺/矽基板並使用變溫砷層來抑制砷化鎵及鍺之間的反向邊界及內部擴散的產生。根據實驗分析結果，成長磷化銦鎵於砷化鎵/鍺/矽基板上的表面粗糙度約為3.5nm，光激螢光的半高寬值約為45nm。於磷化銦鎵/砷化鎵/鍺/矽的磊晶成長過程中，我們也觀察到磷化銦鎵/砷化鎵的接面有差排(差排密度約為9x107/cm2)的形成，這現象可能來自於成長過程中非最佳化的氣體切換設計及砷化鎵磊晶層存在著些許差排所致。

Si substrates as an alternative template, which is used in place of expensive and traditional Ge substrates, will become important trend for the development of low-cost and high-conversion efficiency III-V solar cells. The interface of InGaP epitaxy grown on GaAs epitaxy plays an important factor during InGaP/GaAs/Ge/Si heterostructure growth. The high-quality InGaP epitaxy grown on GaAs/Ge/Si substrates will further enhance the performance of III-V solar cell/Si devices. In this thesis, we firstly use metalorganic chemical vapor deposition (MOCVD) to grow InGaP on GaAs substrates, which help us to get basic parameters and material properties for InGaP/GaAs epitaxial growth, and then transfer to GaAs/Ge/Si substrates using graded-temperature arsenic prelayer suppressing antiphase boundary (APBs) and interdiffusion between GaAs and Ge epitaxy. According to experimental results, the root mean square (RMS) roughness of InGaP on GaAs/Ge/Si structure was about 3.5nm, and the full width at half maximum (FWHM) in photoluminescence (PL) peak was about 45nm. We also observed the formation of dislocation at the InGaP/GaAs interface (dislocation density~9x107/cm2) during InGaP/GaAs/Ge/Si growth. This phenomenon may be due to unsuitable gas-switching sequence during material growth and few dislocations in GaAs epitaxy.