本論文針對提升三五族化合物半導體AlGaInN太陽能電池效率的研究與製作，探討其對太陽能電池元件操作表現的影響，並藉由改變緩衝層(buffer layer)的條件，改善氮化鎵材料成長於藍寶石基板的材料品質。緩衝層厚度為4 μm且主動層為GaN/InGaN(厚度分別為40 Å/30 Å, 28對超晶格)的元件較緩衝層厚度為2 μm時有較佳的光電轉換特性，其JSC、VOC、FF以及η分別為1.03 mA/cm2、1.86 V、43%以及0.82%。主要是因為緩衝層為厚度2 μm的薄膜品質不佳，過多的漏電路徑造成VOC偏低，缺陷所形成的載子殺手(carrier killer)會造成光電流的損耗。當AlGaN/InGaN作為元件主動層時，由於AlGaN/InGaN產生的自發極化(Spontaneous polarization, PSP)與壓電極化(Piezoelectric polarization, PPZ)現象所營造的內建電場比GaN/InGaN來得大，使得照光所產生的電子電洞對可順利的跨越主動層而導到外部電路，因而有效提升太陽能電池元件的操作表現。主動層為Al0.14Ga0.86N/In0.21Ga0.79N(厚度分別為40 Å/30 Å, 14對超晶格)的元件有最佳的操作表現，其JSC、VOC、FF以及η分別為0.84 mA/cm2、2.10、66%以及1.16%。

This study focuses on enhancing the power conversion efficiency of AlGaInN-based photovoltaic (PV) devices of group III-nitride compound semiconductors. PV structures of p-GaN/i-layer/n+-GaN were grown on GaN/sapphire template substrates using a metalorganic vapor-phase epitaxy reactor. PV devices with the GaN/InGaN (40 Å/30 Å for 28 pairs) superlattice (SL) i-layer grown on 4 μm-thick u-GaN template substrates exhibited better performance than devices grown on 2 μm-thick substrates. This can be attributed to the fact that the 4 μm u-GaN material exhibited less TD density than did the 2 μm u-GaN material; hence, the leakage in the current paths was reduced. Sample B4 with the GaN/InGaN (40 Å/30 Å for 28 pairs) SL active i-layer exhibited a short-current density (JSC), open-circuit voltage (VOC), fill factor (FF), and power conversion efficiency (η) of 1.03 mA/cm2, 1.86 V, 43%, and 0.82%, respectively.
As the AlGaN/InGaN SL absorption layers were applied to the active i-layers, the spontaneous and piezoelectric polarization in AlGaN/InGaN heterostructures were both larger than that in the GaN/InGaN heterostructures. The improved polarization can enhance the extraction of photogenerated carriers from the active layers before they were recombined or scattered by TD defects. Sample D1 with the Al0.14Ga0.86N/In0.21Ga0.79N (40 Å/30 Å for 14 pairs) SL active i-layer exhibited JSC, VOC, FF, and η of 0.84 mA/cm2, 2.10 V, 66 %, and 1.16 %, respectively.

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