摘要
本論文針對以液相磊晶系統成長之摻鏑砷化鋁鎵磊晶層做各種特性研究，並研製異質接面之砷化鎵太陽電池。 近年來，全球材料短缺，價格上漲，材料的取得益發困難，在成長磊晶層時，我們採用回融的方法來成長pn接面，不僅材料可以節省一半，更能成長出約0.1um極薄的窗口層，大大改善了在水平式液相磊晶系統之超冷卻(supercooling)方法成長磊晶層的厚度。 對於摻雜鈥的的磊晶層，我們使用了Nomarski顯微鏡、X-ray 繞射、光激螢光、霍爾量測和C-V量測來了解鏑對砷化鋁鎵的影響，並期盼建立P型摻雜的莫耳數和載子濃度關係的完整參數。更以此為基礎，研製異質接面砷化鎵太陽電池。電極是以金屬蒸鍍機來蒸著，並使用lift-off的方法來製作表面電極，元件完成後以I-V量測，藉此了解稀土元素摻雜對太陽電池的影響。 根據實驗結果顯示，當摻雜0-0.024重量百分比的鏑於砷化鋁鎵時，可以得到鏡面的表面。由X-ray繞射量測得出，在微量0.05wt%摻雜時，有較好的結晶性，此外更比較由本研究室歷年來成長摻雜鈥、鏑、釹於砷化鋁鎵中的X-ray量測，更可明顯得到，稀土元素的摻雜需在微量時(約小於0.1wt%)才能改善磊晶層品質。光特性由光激螢光光譜儀獲得，得知鏑的摻雜量和波長與半高波寬有相當的關係，造成波長紅位移效應和半高波寬的減小，此外，載子吸附效應亦得以證明。室溫下的載子濃度、移動率，亦由凡得包法的霍爾效應量測獲得，得到在鏑摻雜P型砷化鎵時，發現摻雜量在0-0.1wt%之間時，濃度有隨著摻雜量增加的趨勢，移動率則隨著摻雜量增加而降低。由C-V量測，得出鏑摻雜於P型砷化鋁鎵層後，濃度可以增加一個order左右，但並不隨摻雜量成正比。元件製作完成後量測I-V並計算出轉換效率為5.17%，於鏑摻雜後效率降低，元件特性並沒有明顯改善。
並列摘要
In this study, the characteristics of the rare-earth element Dy-doped AlGaAs epitaxial layer grown by liquid phase epitaxy was investigated. Taking it as base to fabricate Al0.65Ga0.35As/GaAs heterojunction solar cell structures by the liquid-phase epitaxy etchback regrowth (LPE-ER). In this work, the lattice mismatch for Dy:AlGaAs epilayer can be negligible in the range of 0-0.024 wt% Dy doped and it has mirrow-like surface morphology. The surface morphology, which is important to the ohmic contact for the device applications, was observed by Nomarski interference contrast microscope (N-DICM). The thickness of the AlGaAs layer was obtained by scanning electron microscope (SEM). An oxide is also observed on the top of epilayer. Crystalline was detected by double crystal X-ray diffraction(DCXD). At 0.05 wt%, AlGaAs epitaxial layers doping Dy can improve the crystal quality. We even compare doping Ho, Nd and Dy, AlGaAs in a small doping range of about 0.05 wt% that the FWHM become narrowed. The optical property was measured by photoluminescence (PL). We obtain the wavelength shifts to longer wavelength with increasing Dy wt% and donor gettering effect. In particular, the results of Hall measurement were shown that the AlGaAs epitaxial layers doped with Dy from n-type changing to p-type. From each Dy-treated condition, we select the best-quality grown epilayer to fabricate solar cells. The C-V measurement shows that when p-AlGaAs is doped with Dy, the carrier concentration can be increased by one order. Finally, solar cells were estimated by simulator measurement. The efficiency of solar cell without doping Dy yeaches 5.17% and conscequently the solar cells doped with Dy attain few improvement.
參考文獻
延伸閱讀
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