鍺／鈀／銀歐姆接觸電極與晶膜掀離砷化鎵太陽能電池應用之研究

Study of Ge / Pd / Ag ohmic contact and its application for Epitaxial lift-off GaAs solar cell.

陳信佑(Xin-You Chen)

中原大學/工學院/電子工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200306

摘要

本論文中，我們使用鍺/鈀/銀的金屬結構於負型砷化鎵上形成歐姆接觸。藉由改變鍺、鈀的厚度及回火條件，並利用傳輸線模型法來調查出最低的特徵電阻率(ρc)。我們發現最佳的金屬結構為鍺(50nm)鈀(80nm)/銀(300nm)，並且在回火條件為攝氏350度及1分鐘下可獲得最低的特徵電阻，其值約 ρc ~7.2×10-6Ω-cm2 。此外實驗結果顯示，鍺/鈀/銀的金屬結構是否形成歐姆接觸取決於鍺/鈀的厚度比例。若鈀的厚度不足則會形成蕭特基接觸或不良的歐姆接觸且厚度不足的鈀要形成歐姆接觸則需較高的回火溫度。
然後將鍺/鈀/銀的最佳金屬結構應用於晶膜掀離砷化鎵/鉬(砷化鎵接合在鉬上)太陽能電池之N型歐姆接觸電極之上。在室溫以一個太陽條件下量測電流-電壓特性。發現鍺(50nm)鈀(80nm)/銀(300nm)金屬結構在攝氏350度及1分鐘的回火條件下，獲得最佳的轉換效率5%。另外我們還研究不同的接合溫度及不同光罩對於晶膜掀離太陽能電池的影響。由實驗結果發現，接合溫度高轉換效率有下降的趨勢，以及在相同的接合溫度下E形光罩(面積為6.85 mm2)的效率比正方形(9.73 mm2)的還好。

關鍵字

歐姆接觸 ； 太陽能電池 ； 晶圓接合 ； 晶膜掀離

並列摘要

In this dissertation, the metallurgical structure of Ge/Pd/Ag is adopted to study the formation of ohmic contact on n-type GaAs material. By changing the thickness of Ge as well as Pd, and the annealing conditions, the best condition for having an ohmic contact with the lowest specific contact resistivity (ρc) is investigated via the use of transmission line method (TLM). We found out that the optimum metallurgical structure is Ge(50nm)/Pd(80nm)/Ag(300nm) which annealed at 350℃ for 1 minute. The lowest value (ρc =7.2×10-6 Ω-cm2) of specific contact resistance could be attained. Additionally, experimental results show that the ratio of Pd/Ge plays an important role in determining the ohmic contact formation in the metallurgical structure of Ge/Pd/Ag such that insufficient Pd metal thickness always results in Schottky contact or fair ohmic contact with an annealing temperature much higher than that having sufficient Pd metal thickness.
Then, the optimum metallurgical structures of Ge / Pd /Ag is applied as n-type ohmic contact for the fabrication of the GaAs/Mo (GaAs is bonded on Mo) Epitaxial lift-off (ELO) solar cell. The current–voltage (I–V) characteristics are measured under one-sun at room temperature. The best conversion efficiency about 5% for ELO solar cell with Ge(50nm) /Pd(80nm)/Ag(300nm) after annealing 350°C for 1 minute is obtained.
Additionally, we also studied different bonding temperature and mask to ELO solar cell influence. The experimental results indicate that the bonding temperature was high and efficiency was declined. And, E-shaped (mask area is 6.85mm2)efficiency is better than square (mask area is 9.73mm2) for same bonding temperature.

並列關鍵字

solar cell ； ohmic contact ； ELO ； wafer bonding

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