應用晶圓接合與磊晶膜剝離技術製作GaAs/Si雙接面太陽能電池之特性探討

Fabrication of GaAs/Si Multi-Junction Solar Cell by Epitaxial Lift-Off and Wafer Bonding

周育正(Yu-Cheng Chou)

指導教授 ： 何文章

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2009年)

摘要

本篇論文說明製作GaAs/Si雙接面太陽能電池以及其特性探討。太陽光譜其波長範圍約在200nm到3000nm，如此寬廣的光譜分佈若只是單一接面太陽能電池吸收並不能有效利用太陽光譜，而多接面太陽能電池使用兩種以上不同能隙的材料作為太陽能電池的吸光材料，如此可以充分有效的利用入射光譜，減少入射光的浪費(Thermal Loss)，並且可以增加太陽能電池的開路電壓(Open-Circuit Voltage, VOC)以及光電轉換效率(Conversion Efficiency, η)。
一般來說異質層太陽能電池多是利用磊晶的方式製作，但在單晶矽上並不能磊晶良好品質的砷化鎵結構，故我們嘗試運用晶圓接合(Wafer Bonding)以及磊晶膜剝離(Epitaxial Lift-off, ELO)的技術，來製作GaAs/Si雙接面太陽能電池。
首先我們先製作出單一砷化鎵太陽能電池以及單一單晶矽太陽能電池，其磊晶層結構與GaAs/Si雙接面太陽能電池相同。其中砷化鎵太陽能電池利用蝕刻之方式將電極製作於同一面，分別鍍上金鋅合金(AuZn)以及金屬銦當作電極；而單晶矽太陽能電池利用蝕刻之方式，將太陽能電池分割成四個區域，於電池正面四個區域分別鍍上不同遮蔽率之鋁電極，背面鍍上鈦鋁(Ti/Al)電極。製作完成之砷化鎵與單晶矽太陽能電池，以AM1.5G太陽光環境下進行元件量測。
其次，我們應用晶圓接合技術使用銦金屬薄膜將砷化镓太陽能電池和矽太陽能電池接合在一起，再來以磊晶膜剝離技術將接合在矽太陽能電池上的砷化鎵薄膜與砷化鎵基板分離，最後將GaAs/Si雙接面太陽能電池之正面以電子束蒸鍍系統鍍上金鋅合金(AuZn)以及背面蒸鍍鈦鋁(Ti/Al)金屬，完成第一階段GaAs/Si雙接面太陽能電池的製作。
我們製作完成之GaAs/Si雙接面太陽能電池以AM1.5G太陽光環境下進行元件量測，再由量測所得之I-V特性曲線，求得四個重要的太陽能電池參數:開路電壓(VOC)、短路電流密度(JSC)、填充因子(FF)以及太陽能轉換效率(η)。

關鍵字

砷化镓太陽能電池 ； 單晶矽太陽能電池 ； 磊晶膜剝離 ； 晶圓接合 ； 電子束蒸鍍

並列摘要

This article show the fabrication of GaAs/Si multi-junction solar cell using the wafer bonding and epitaxial lift-off (ELO) techniques. Typically, the wavelength of solar energy is from 200nm to 3000nm. If we use single junction in solar cell to absorb all solar energy, it is not efficiency because the thermal loss. However, multi-junction solar cells can improve and make better use of the solar spectrum due to having multiple semiconductor layers with different band-gaps in cells. So that the advantage of multi-junction solar cell is reducing loss of incident light, increasing open-circuit voltage (Voc) and increasing conversion efficiency (η).
Usually, the multi-junction solar cell is using hetero epitaxial growth by MOCVD. This method can not have a good quality of GaAs films growth on on Si. We try to solve this problem and use wafer bonding and epitaxial lift-off process to fabricate a GaAs/Si multi-junction solar cell.
At first, we use the same wafer similar to multi-junction solar cell to fabricate a GaAs solar cell and a Si solar cell. For GaAs solar cell, we etch GaAs wafer to let GaAs emitter layer on surface and deposit AuZn and In as electrodes respectively. For Si solar cell, we use etching Si wafer for isolation, depositing different shadowing of Al front electrodes and depositing Ti and Al electrodes on the back side. The fabricated GaAs solar cell and Si solar cell be measured under a simulated AM 1.5G condition respectively.
Secondly, we use thin film of indium to connect GaAs wafer and Si wafer by wafer bonding, and then separating GaAs substrate from GaAs/In/Si device by epitaxial lift-off, and depositing AuZn on front side and Ti/Al on back side respectively.
Finally, the fabricated GaAs/Si multi-junction solar cell wafer was measured under a simulated AM 1.5G condition. From result of I-V measurement, we can find four kinds of solar cell parameter including: open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and conversion efficiency (η).

並列關鍵字

Gallium Arsenic Solar Cell ； Silicon Solar Cell ； Epitaxial Lift-Off ； Wafer Bonding ； Electron Beam Evaporator

參考文獻

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