以射頻磁控濺鍍法製備低阻值之P型氧化鋅薄膜

Fabrication of p-type ZnO thin film with low resistivity by RF magnetron sputtering

吳信毅(Shin-Yi Wu)

指導教授 ： 盧陽明

共同指導教授 ： 莊賦祥(Fuh-Shyang Juang)

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2008年)

摘要

氧化鋅(ZnO)為目前很有潛力的光電半導體材料之一，具有易蝕刻、無毒性、價廉等優點，由於目前的ZnO多屬於n-type的半導體氧化物，如果能成功研發p-type的ZnO與n-type的ZnO搭配，將可開發出ZnO的全新光電半導體應用領域。然而在p型氧化鋅薄膜上仍有許多問題存在，例如氧離子會捕捉正電洞與之形成不具電活性的複合缺陷及授體(donor)雜質的低解度，導致p-ZnO薄膜導電度不佳，或是薄膜內部缺陷(defects)所造成的發光、以及電性穩定度等問題；故本研究想藉由摻雜鋰原子於氧化鋅薄膜之中，以製備p型氧化鋅薄膜及改善薄膜導電性質。
本論文是以射頻濺鍍系統(RF sputter)，利用鋅鋰合金靶並再貼附碳酸鋰片結合之複合靶材材料，沉積不同鋰含量之氧化鋅材料於玻璃基板上，藉由不同鋰片數，以得到不同導電性質之氧化鋅薄膜。接著利用霍爾量測系統(Hall measurement)、可見光光光譜儀(UV-Visible)系統、原子力顯微鏡(AFM)系統、感應耦合電漿質譜分析儀(ICP-MS)、低角度X-ray繞射系統(GIAXRD)，分析薄膜成份結構及光電特性的探討。
研究結果分析顯示，薄膜經由熱探針量測，確實為p-type，其結果與霍爾量測數據相同，摻雜鋰於氧化鋅能有效得到p型氧化鋅。經由GIAXRD結構分析，不同鋰量的掺雜下，並不會影響氧化鋅之結晶特性，由結果顯示，ZnO:Li薄膜具有(002)面之優先取向繞射峰。當掺雜Li量小於11.1at%時，氧化鋅(002)繞射峰值往高角度偏移，即Li有效取代Zn在ZnO中的晶格位置(因為Li原子半徑小於Zn原子半徑)；但當Li掺雜量大於11.1at%時，氧化鋅(002)繞射峰值往低角度偏移，則鋰原子反而進入間隙位置，使晶格面間距變大。在導電性質方面，最低電阻率為4.72×10-1 ohm-cm，是在鋰摻雜量為11.1at%時 。在光學穿透特性方面，p-type ZnO的可見光穿透率大多可維持在70-80%。

關鍵字

氧化鋅 ； 濺鍍 ； p-type

並列摘要

The ZnO thin film has been of great interest because of potential applications for optoelectronic devices. However, a p-type ZnO film conduction with low resistivity is difficult to achieve because of self-compensation effect of the opposite charge carriers and low solubility of the doping acceptors.
In this work, Lithium-doped ZnO films were grown on glass substrates by RF reactive magnetron sputtering using Zn:Li metal alloy target with several Li2CO3 piece on it. Then, zinc oxide film compositions were determined by ICP-MS. Elemental depth profiles were employed by SIMS analysis. The structure and crystallinity of zinc oxide films, the GIAXRD were used to characterize. Hot probes and Hall measurement were used to determined resistivity, carrier density and mobility. The UV-Visible spectrophotometer was used to measure the transparency of zinc oxide films with various wavelengths.
The GIAXRD analysis indicates that the ZnO:Li films have (002) preferred orientation. The optical transmission spectra show a high transmittance (~80%) in the visible region. The lowest resistivity of as-grown p-type ZnO:Li film is 4.72×10-1 ohm-cm. A p-type conductive behavior was confirmed by the hall-effect measurement for these ZnO:Li films with a carrier concentration of 2.47×1019cm-3 and hall mobility of 0.85 cm2/V-sec.

並列關鍵字

ZnO ； sputtering ； p-type

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