熱退火對鈣摻雜銅鋁氧化物材料及異質接面二極體影響之研究

The study of thermal annealing effect on Ca doped CuAlO2 material and heterojunction diodes

黃柏崴(Bo-Wei Huang)

指導教授 ： 陳建彰

共同指導教授 ： 陳奕君(I-Chun Cheng)

國立臺灣大學/工學院/應用力學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.10394

摘要

銅鋁氧化物為深具潛力的P型透明導電材料。在室溫沉積之銅鋁氧化物呈現非晶態，故本研究嘗試以Ca摻雜來降低薄膜電阻率，並探討熱退火對薄膜材料以及二極體元件的影響。
　　本實驗利用射頻磁控濺鍍機，於室溫下沉積不同Ca摻雜濃度之銅鋁氧化物薄膜。從低掠角繞射儀(GIXRD)分析未退火薄膜結構成非晶態，並以EPMA來分析薄膜成分。本研究同時以XPS分析未退火薄膜中Cu+離子以及Cu2+離子的含量，以界定未退火薄膜中的鍵結狀況。在電性方面，以CuAl0.8Ca0.2O2靶材於純氧的氣氛下沉積之薄膜具有最低的電阻率；於純氧下沉積未退火之CuAl0.8Ca0.2O2薄膜經由霍爾量測，其載子遷移率為1.02 cm2/V-s，載子濃度為1.289×1017 cm-3 ，霍爾係數為69.2 m2/C，導電率為0.02 S-cm-1。量得之Seebeck係數為230 (μV/K)，証實確有P-型導電之性質。之後我們進一步將未退火之CuAl1-xCaxO2薄膜製作成異質接面二極體，且發現在Ar:O2=15:10的氣氛下沉積且未退火之CuAl0.8Ca0.2O2薄膜與剛沉積之AZO 3wt%薄膜具有最佳的整流性質。CuAl0.8Ca0.2O2 / AZO 3wt% 所形成之二極體，其崩潰電壓為-4.04 V，啟動電壓為 0.8V，而整流值為273。
　　薄膜在退火至600oC 結晶尚不明顯，且電阻率也大幅上升，較未退火薄膜電阻率來得高出許多。在退火至900oC之後的CuAl1-xCaxO2薄膜並非純的銅鋁氧化結晶相，且由SEM中觀察到析出物的產生。在Ar:O2=15:10的氣氛下沉積且退火至900oC之CuAl0.8Ca0.2O2薄膜其電阻率為276 Ω-cm。由實驗中我們發現，Ca的摻雜取代Al會使銅鋁氧化物的結晶相較不容易形成，此一現象隨著Ca濃度上升而更明顯。之後我們將退火900oC之CuAl1-xCaxO2薄膜與AZO 3wt%製作成二極體元件，退火至900oC之CuAl0.8Ca0.2O2 / 剛成膜之AZO 3wt% 所形成之二極體，其崩潰電壓為-1.73V，啟動電壓為2.66V，而整流值為0.25。

　　由本實驗我們發現未退火之CuAl1-xCaxO2薄膜與AZO 3wt% 有較佳的二極體曲線，且透過霍爾量測以及熱電量測驗證Ca摻雜CuAlO2薄膜在室溫濺鍍下會具有P型的導電性質。
　　本實驗中，退火至900oC之CuAl1-xCaxO2薄膜不是純的銅鋁氧化物結晶相。為了製作出純的銅鋁氧化物，我們透過調變Al在靶材中的濃度。我們設計了CuAlx-0.2Ca0.2O2 (=1.25、1.75、2) 的靶材參數，將CuAlx-0.2Ca0.2O2沉積於石英基板上，並於氮氣中退火至900oC，持溫5小時。最後我們透過GIXRD發現當x達1.75時，在Ca摻雜的情況下會有純的銅鋁有化物相的產生。

關鍵字

透明導電薄膜 ； P型 ； 銅鋁氧化物 ； 異質接面二極體

並列摘要

Copper aluminum oxide is one of potential candidates for P-type transparent conducting oxides. In this study, the films are deposited using RF-sputtering technique. The as-deposited copper aluminum oxide thin films are amorphous. Calcium is introduced to reduce the resistivity of the thin films. We also investigate the influence of thermal annealing effect on the characteristics of calcium doped CuAlO2 thin films and heterojunction diodes.
The films are deposited using RF-sputtering technique with one compound target at room temperature. From the results of glancing angle X-ray diffraction the as-deposited calcium doped CuAlO2 thin films are amorphous. Film compositions are evaluated by wavelength dispersion spectroscopy, and the compositions of Cu+ and Cu2+ are identified by XPS. CuAl0.8Ca0.2O2 sputter-deposited under O2 ambient exhibit lowest electrical resistivity. The carrier concentration is 1.02 cm2/V-s，carrier density is 1.289×1017 cm-3 , hall coefficient is 69.2 m2/C, conductivity is 0.02 S-cm-1. Seebeck coefficient of as-deposited CuAlO2 thin film is 230 μV/K. P-N diode of as-deposited CuAl0.8Ca0.2O2 /AZO 3wt% exhibits best diode properties. The turn on voltage is 0.8V and breakdown voltage is -4.04 V and the rectifying ratio is 273.
The crystallinity of 600 oC×5hr annealed thin films can not be observed using GIXRD. The resistivity of the 600 oC×5hr annealed thin film is also higher than as-deposited one. When the annealing temperature is raised to 900 oC, the crystalline phase is not pure CuAlO2. The precipitates can also be observed using SEM. The resitivity of 900oC annealed CuAl0.8Ca0.2O2 is around 276 Ω-cm. The substitution of Al with Ca deteriorates the phase formation of CuAlO2 ; the amount of CuAlO2 phase decrease as the Ca concentration increases. 900oC annealed CuAl1-xCaxO2 is used with 3wt% AZO to form heterojunction diodes. The breakdown voltage is around -1.73 V; the turn-on voltage is around 2.66 V; the rectifying ratio is around 0.25.

　　The diodes fabricated using room temperature deposited CuAl1-xCaxO2 and 3wt% AZO exhibit better diode performance. Through Hall measurement and seeback coefficient measurement, it is verified that room temperature sputtered CuAl1-xCaxO2 reveals P-type conductivity.
To obtain pure phase CuAlO2 thin film, the Al content in the target is varied. Targets of CuAlx-0.2Ca0.2O2 (x=1.25, 1.75, 2) are used for the film deposition on quartz substrates. After 900oC×5hr thermal annealing in N2 , we obtain pure phase CuAlO2 thin films using CuAl1.55Ca0.2O2 target, verified by GIXRD.

並列關鍵字

TCO ； p-type ； CuAlO2 ； heterojunction diodes

參考文獻

第一章參考文獻

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