本論文是針對氧化鋅鋁摻雜釔(AZO:Y2O3;AZO:Y)之透明導電薄膜，對其光電特性進行一系列的量測分析，以其在P型氮化鎵(P-GaN)上之歐姆接觸特性研究，並將此薄膜成長在氮化鎵藍色發光二極體上與傳統之透明導電膜-氧化銦錫(ITO)相互比較，探討其光電特性之差異。
本實驗採用的是濺鍍(sputtering)系統來成長薄膜。由實驗可得，當直流功率為150瓦成長之AZO:Y薄膜，在氮氣環境下700℃熱處理1分鐘時，有最低電阻率為6.898×10-4Ω-cm，而遷移率(mobility)為25.1cm2/V-s及載子濃度(carrier concentration)為-3.61×1020cm-3。經熱處理後，在可見光波段380nm~700nm，其平均穿透率皆可高於85%。且其光吸收邊界(optical absorption band)有明顯的藍移(blue shift)現象，此現象乃是因載子濃度的提高所造成的柏斯坦-摩斯效應(Burstein-Moss effect)。
將所得之AZO:Y薄膜作為P型氮化鎵上之透明電極，與傳統之ITO透明電極比較。AZO:Y薄膜直接成長在P型氮化鎵上無法得到線性之歐姆接觸特性，但在700℃熱處理1分鐘時，有最佳之電流-電壓特性，其特徵接觸電阻(ρc)為1.45×10-1Ω-cm2。ITO透明電極在氮氣環境下600℃熱處理5分鐘時，有線性之歐姆接觸特性，其特徵接觸電阻(ρc)為7.80×10-2Ω-cm2。
經由比較不同的透明導電膜(ITO、AZO:Y、ITO/AZO:Y)在氮化鎵藍色發光二極體上之光電特性可發現。在20mA注入下，ITO與AZO:Y發光二極體其順向導通電壓(Vf)分別為3.37V與3.55V，且其光輸出功率(light output power)分別為3.59mW與3.96mW。AZO:Y發光二極體其導通電壓約只高出ITO發光二極體0.2V，但其光輸出功率則增加了約10%。
藉由在p-GaN與AZO:Y透明導電膜之間，成長一層ITO可有效的改善歐姆接觸特性，進而降低發光二極體之導通電壓。在20mA注入時，ITO/AZO:Y發光二極體其順向導通電壓(Vf)為3.2V比AZO:Y發光二極體 Vf為3.55V，可成功降低約0.35V。
經由本研究可知，AZO:Y薄膜因具有高光穿透率與良好之電流散佈效果，因此可替代氧化銦錫(ITO)來當成透明導電膜應用在氮化鎵發光二極體(GaN-based LED)上的潛力。

In this study, transparent and conductive AZO:Y2O3 (AZO:Y) thin films are performed as the potential transparent contact layer on nitride-based light emitting diodes.
When the DC power of 150W, it showed a lowest resistivity of 6.89×10-4 Ω-cm and a carrier concentration of 3.61×1020 cm-3 and a mobility of 25.1 cm2/V-s that the thermal annealing at 700C for 1 min in nitrogen ambient. And the AZO:Y films showed high transmittance (>85%) in the visible wavelength range after thermal annealing.
We had demonstrated the AZO:Y films and ITO films as ohmic contacts on p-type GaN . The I-V characteristic of AZO:Y contact on p-GaN was not a perfect ohmic property after thermal annealing. And the ITO contact on p-GaN was an ohmic property after thermal annealing at 600°C for 5min in nitrogen ambient. The lowest specific contact resistance of AZO:Y and ITO contact on p-GaN was 1.45×10-1 and 7.8×10-2Ω-cm2, respectively.
GaN-based LEDs with ITO and AZO:Y contact layers were fabricated for the optoelectrical characteristics study. The forward voltage (light output power) was 3.375 V (3.59mW) and 3.55 V (3.96mW) for the LEDs with ITO and AZO:Y contact layer under 20mA current injection, respectively. The forward voltage of the LED with AZO:Y contact layer was slightly higher 0.2V than the LED with ITO contact under 20mA current injection. However, the light output power of the LED with AZO:Y contact layer is larger 10% than the LED with ITO contact under 20mA current injection.
Inserting the ITO contact layer between p-GaN and AZO:Y can be improved the electrical properties of LEDs. The forward voltage of LED with ITO/AZO:Y contact layer was 3.2V under 20mA current injection and was successfully 0.35V lower than the LED with AZO:Y contact.
These results revealed that the AZO:Y film is promising as alternative to ITO for transparent electrode application on GaN-based light-emitting diode.

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