以有機化學氣相沉積法成長氧化鋅摻雜鎵之透明導電薄膜其特性及元件應用之研究 ; Characteristics and device applications of Ga-doped ZnO transparent conductive layers grown by MOCVD

本研究利用有機金屬化學氣相沉積系統(metal-organic chemical deposition, MOCVD)在藍寶石(sapphire)基板上成長摻鎵氧化鋅(Ga-doped Zinc Oxide, GZO)透明導電薄膜。探討不同的TMGa流量及退火溫度對薄膜結晶特性、光學特性以及導電特性之影響及其相關性。最後利用MOCVD將GZO透明導電薄膜應用於藍光GaN-LED。經由快速熱退火(Rapid Thermal Annealing, RTA)進行退火，使GZO/p-GaN接面達到歐姆接觸，並討論GZO-LED的元件電特性及發光特性。 由研究發現，TMGa流量為10 sccm成長之GZO薄膜，其電阻率可達2.41×10-3 Ω-cm。將GZO薄膜於氮氣環境600 oC下進行退火製程後，其薄膜結晶品質及載子濃度將會有明顯提升。GZO薄膜的電阻率最低可達3.38×10-4 Ω-cm，載子遷移率為6.4 cm2/ V-s載子濃度為2.94×1021 cm-3，於藍光450 nm波長穿透率提升至97%以上，相較於常見的ITO薄膜具有相近的電特性及更高的穿透率。 最後利用MOCVD將GZO透明導電薄膜應用於藍光GaN LED。經由退火製程後發現在GZO/p-GaN接面的部份，有Zn原子擴散進入p-GaN表層，進而促進GZO/p-GaN接面的歐姆特性。GZO-LED元件特性在20 mA電流注入下具有70%的外部光取出效率，在350 mA的電流注入下具有251.5 mW的輸出功率，相較於常見的ITO-LED可以有8.5%的提升。以上結果顯示了經由MOCVD成長GZO薄膜在GaN LED上的應用性及可行性。 ; In this study high performance of Ga-doped ZnO (GZO) films have been prepared on sapphire substrates by the metal-organic chemical deposition (MOCVD) We focus on the optimization of the electrical and optical properties of GZO films by varying TMGa flow rate It was found that the resistivity of as-deposited GZO thin films deposited with TMGa flow rate 10 sccm was 2 41×10-3 Ω-cm After thermal annealing in 600 oC for 2 min in N2 ambient the resistivity of GZO could be as low as 3 38×10-4 Ω-cm It was attributed to the improvement of the GZO crystal quality leading to an increase in electron concentration It was also found that the optical transmittance of GZO thin films exhibited a high transparency above 97% at wavelength of 450 nm Ga-doped ZnO (GZO) were deposited by MOCVD to be the transparent contact layers(TCL) for GaN blue light-emitting diodes (LEDs) The contact resistance of GZO decreased with the annealing temperature increasing It was also found that some Zn atom caused from the decomposition process diffused into the p-GaN surface of LED which generated a stronger tunneling effect at the GZO/p-GaN interface and promoted the formation of ohmic contact Moreover contrast to the ITO-LED a high light extraction efficiency of 77% was achieved in the GZO-LED at injection current of 20 mA At 350 mA injection ...