以奈米孔隙透明導電膜優化奈米矽金氧半發光二極體之研究

Abstract

在本論文中討論了退火造成氧化銦錫和鎵參雜的氧化鋅薄膜的優化。氧化銦錫在退火後，其晶相轉為柱狀晶且同時提升錫氧鍵吸收，大大降低其電阻率至1.2x10-4 歐姆-公分。45奈米的鎵參雜氧化鋅的電阻率降低至1.8x10-2 歐姆-公分並在紫外光至可見光區域保有超過95%的穿透率，鎵參雜氧化鋅在可見光區擁有較佳的穿透率 (大於80%)，但是反觀電阻率，由於過多游離鎵雜質造成嚴重的散射，就算結構晶相提升也無法補償此劣化，因此鎵參雜的氧化鋅卻比氧化銦錫高了兩個數量級。將兩薄膜的電性跟光性做比較，氧化銦錫薄膜擁有較低的電阻率以及保有還不錯的穿透率，仍是較佳的選擇。此外，多孔性陽極氧化鋁可以以草酸為電解液用兩次陽極氧化法得到，擴孔步驟是為了去除底部的阻隔層，在500度退火後可將缺陷去除，再將此應用到矽基金氧半發光二極體作為表面粗糙層，可得到擁有氧化銦錫及多孔隙陽極氧化鋁覆蓋的矽基金氧半發光二極體，比較此兩者的效率，擁有孔隙氧化鋁的元件在1100度退火後有較低的起始電壓為130伏特，以及較低的1.25電子伏特等效能障，其最大發光功率為544奈瓦並有著較大的功率-電流斜率和內部量子效率分別為0.598毫瓦每安培和0.059%， 其最佳電光轉換效率和外部量子效率分別為1.78x10-4 %及0.027%，其效率比傳統結構還要高。

In this thesis, the annealing induced optimization on transmittance and resistivity of the sputtered ITO and GZO films are compared. After annealing, the ITO transforms its crystallinity from amorphous to columnar nano-grains and enriches the Sn-O bonds absorption to greatly reduce its resistivity to 1.2x10-4 Ohm-cm. The resistivity of 45-nm GZO film reduces to 1.8x10-2 Ohm-cm, while the UV-VIS transmittance remains at > 95%. The GZO film exhibits a higher optical transmittance than ITO film in visible light region (> 80%). However, its electrical resistivity is two orders of magnitude higher than that of ITO film. The higher resistivity is mainly attributed to the serious carrier scattering by ionized impurity of the redundant Ga, and even annealing induced crystallinity is unable to compensate the deterioration. In view of the optical and electrical performance of both GZO and ITO film, the compromised optical and electrical property of ITO film is preferable with relatively low resistivity and quite good UV-visible transmittance. Moreover, the formation of porous AAO on p-Si substrate is demonstrated with two-step anodization in oxalic solution. Pore-widening process is required to remove the barrier oxide layer. Defects are suppressed after post annealing of 500oC. After applying the porous AAO to the conventional Si-based MOSLD as a surface roughness layer, the ITO/AAO covered MOSLED is fabricated. In comparison with the conventional and the ITO/AAO covered MOSLED, the latter demonstrates a lower turn-on voltage of 130V, and lower effective barrier height of 1.25 eV after 1100oC annealing. Hence, the maximal output power of ITO/AAO covered sample is 544 nW with corresponding P-I slope and internal quantum efficiency of 0.598 mW/A and 0.059% while the conventional one is a little lower. The power conversion ratio of 1.78x10-4% and external quantum efficiency of 0.027% are also higher at the ITO/AAO covered MOSLED.