砷化鎵單接面太陽電池晶圓接合與磊晶膜掀離之研究

Study of Wafer Bonding and Epitaxial Lift-Off to GaAs Single Junction Solar Cell

楊秉棠(Bing-Tang Yang)

中原大學/工學院/電子工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200520

摘要

摘要
在本論文中，我們在負型矽基板上沉積鈀/銀/金結構，並且改變不同的鈀層厚度，利用傳輸線模型法計算出歐姆接觸結構之特徵接觸電阻率，藉此來評估此歐姆接觸結構之可行性。實驗結果顯示，當鈀層厚度從25nm增加到50nm時，最低特徵接觸電阻率出現之回火溫度從450℃下降到375℃;當鈀層厚度增加到100nm時，最低特徵接觸電阻率出現之回火溫度從375℃上升到425℃。鈀(50nm)/銀(300nm)/金(30nm)結構在回火條件375℃兩分鐘下，可以得到最佳的特徵接觸電阻率 ρc ~ 2.7x10-6 Ω-cm2。更進一步，我們改變鈀/銀/金結構的回火溫度與時間，測試不同條件下對於HF的耐蝕刻性。實驗結果顯示，當鈀層厚度為25nm時，提高回火溫度與延長回火時間對於鈀/銀/金結構的耐蝕刻性是必須的。
透過以上實驗結果，我們將最佳化歐姆接觸結構應用至矽基板，利用晶圓接合技術和砷化鎵單接面太陽電池進行接合，接著利用磊晶膜掀離技術將砷化鎵太陽能電池結構與砷化鎵基板分離，完成砷化鎵薄膜結構鍵結在矽基板上的異質結構，並且探討此太陽電池之特性表現。實驗結果顯示，太陽電池的開路電壓、短路電流、填充因子以及轉換效率表現並不理想，其原因可能出於元件製程部分，其相關機制仍在研究進行中。

關鍵字

磊晶膜掀離 ； 砷化鎵單接面太陽電池 ； 晶圓接合

並列摘要

Abstract
In this thesis, a metal structure of Pd/Ag/Au is employed to form an ohmic contact to the n-Si substrate with the annealing temperature and the metal thickness of Pd being varied to optimize the metal structure. The feasibility of the metal structure is examined by analyzing the specific contact resistivity (ρc) deduced from the simple contact resistance measured through transmission line method (TLM). Experimental results indicate that the annealing temperature for obtaining the lowest ρc is decreased from 450 to 375℃ with increasing film thickness of Pd from 25 to 50 nm. Once the Pd layer is increased to 100 nm, the most appropriate annealing temperature for the metal structure is increased from 375 to 425℃. Ultimately, an optimal metallurgical structure of Pd(50nm)/Ag(300nm)/Au(30nm) with a considerably low ρc ~ 2.7x10-6 Ω-cm2 can be obtained after the annealing is conducted at 375℃ for 2 min. Furthermore, the resistance of the deposited metallurgical structures against HF solution after different annealing treatments were investigated. The results show that sufficient annealing temperature and time for the metal structures with a constant Pd layer of 25 nm are essential for them to refrain from the etching of HF solution.
Based on the results measured by TLM, the optimum metallurgical structure Pd(25nm)/Ag(300nm)/Au(30nm) was applied to n-Si ohmic contact. We used wafer bonding technique to bond Si substrate and GaAs single junction solar cell together, and then used epitaxial lift-off technique to separate GaAs thin film structure from GaAs substrate. Finally, a heterostructure GaAs single junction solar cell was fabricated. We measured the solar cell parameters of the solar cell, including the open circuit voltage, short circuit current, fill factor, and conversion efficiency. The results indicated that the solar cell performance was out of expectation. We consider the problems to be possibly caused by the device fabrication process, and study of the details is still underway now.

並列關鍵字

GaAs single junction solar cell ； epitaxial lift-off ； wafer bonding

參考文獻

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