【作者】 杨洪军；

【导师】 杜国同；

【作者基本信息】 吉林大学 ， 微电子学与固体电子学， 2004， 硕士

【摘要】 ZnO 材料是一种宽禁带的多功能半导体光电材料，在许多领域都具有广泛的用途。例如，可用于制作紫外发光管和激光器、紫外探测器、高频表面声波器件、透明导电电极和声光换能器等，所以一直倍受研究人员的关注。特别是 1996 年， ZnO 薄膜室温光泵浦紫外激射的获得，又掀起了研究 ZnO材料尤其是 ZnO 薄膜的热潮。随后 ZnO 薄膜材料的研究工作不断取得进展。许多研究小组先后报道了 P 型材料的制备，氧化锌 PN 结和发光管的实现，以及 ZnO 的多元合金材料研究，低损、高频 ZnO 基表面声波滤波器的应用等。本论文以 MOCVD 制备方法为基础，系统的研究了 ZnO 多层薄膜结构的生长特性，分析了这些结构的突出特点，并有针对性的制备了高频声表面波滤波器件，获得了较好的结果。 本文系统地阐述了ZnO在结构、压电方面的特性；研究了以ZnO为基础的声表面波器件的基本特性，指出了高阻和平整的表面结构是制备声表面波器件的基本条件；分析了适合制备高频、低损声表面波器件所需的衬底材料；针对多层结构分析了器件的频率和温度特性；介绍了适合制备高质量ZnO 薄膜的新型等离子增强MOCVD 系统。该系统有许多创新之处，如利用DEZn和O2为源，采用分开通气方法，通过面向衬底座的喷枪通源；采用均匀结构电阻式加热器；采用无极变速高速旋转的衬底座；利用辅气路均匀下压气流抑制热上升气流等。该系能有效抑制预反应问题；解决了薄膜的生长均匀性问题；可利用等离子体发生装置对薄膜进行有效掺杂；适合制备高阻或P型ZnO 薄膜。 首次使用MOCVD法在金刚石单晶衬底上生长了ZnO薄膜结构，使用气流两步法对生长进行了优化，X光衍射谱图表明薄膜具有单一的趋向性。表面分析表明慢速生长有利于籽晶的长大，PL谱分析和光吸收分析证实了样品具有较强的紫外发射峰，通过生长的优化后内部的缺陷浓度得到了相应的减少。通过拉曼散射测试进一步证明生长的ZnO/Diamond薄膜具有一定的组群对称性。 在 MOCVD 法 生 长 中 ， 通 过 生 长 温 度 和 气 流 的 调 整 ， 改 善 了 1<WP=59>吉 林 大 学 硕 士 学 位 论 文ZnO/Diamond/Si结构的薄膜质量，使晶粒取向性得到了改善。通过表面扫描电镜的分析对样品的表面形貌进行了分析。PL光谱比较分析表明，低温生长的薄膜紫外发光质量很差，而高温生长的样品中存在不同强度的深能级发光峰。不同样品的光电子能谱对比表明通过优化，样品中与氧缺陷有关的峰逐渐减弱，对于最终的样品获得了较好的化学计量比。电学测试显示高温下的样品具有高阻和弱P型导电特性。 使用ZnO/Diamond/Si结构制备了声表面波滤波器件，获得了高阶模滤波频率0.8GHz的高频SAW滤波器。分析了不同波长和膜厚的器件对频率特性的影响，通过理论和实验分析表明，使用金刚石衬底后，表面波传播波速得到提高，滤波器的中心频率从600M上升到870M左右，分析表明在使用精细的光刻技术后，使用金刚石衬底有利于制备频率超过GHz的高频表面声波器件。 2更多还原

【Abstract】 ZnO is a direct wide-band gap semiconductor optical-electronic material with manyapplications, such as in ultraviolet laser, low-loss high-frequency surface acoustic wave (SAW)devices, buffer layers for III-nitride growth, and transparent electrode et al, which make itmore attractive to many research groups for a long time. Especially in 1996, the upsurge inZnO research is coming due to the realization of the light pumped exciton emitting anddiscovery of self-formed cavity. Subsequently, some groups make more progress in formationof the p type ZnO and p-n devices, the work in multi-element alloy materials were alsoexpanded. In this paper, high quality ZnO thin films on different substrates have beenobtained by MOCVD system designed for SAW application. At the same time, the propertiesand devices of SAW for ZnO films have been investigated in details, and good results havebeen achieved. First, the characteristics of the structure and piezoelectric are studied systematically bythe author, especially for the SAW filter of ZnO. It concluded that the smoother surface andhigh resistivity were the first requisite of high performance SAW filter. The different substratematerials for SAW were discussed in this chapter, in which the diamond substrate is preferredfor high frequency SAW device. The frequency and temperature characteristic were studiedfor multi-layer ZnO structure also. According to the principle of MOCVD and in order to solve the problem in ZnO growthprocess, new-type plasma enhanced MOCVD system has been designed and fabricated. Theprecursors ( DEZn and O2 ) have been introduced into the reactor by two gas lines,respectively. And the precursors arrive to the surface of sapphire substrate by two separatedspecial injectors. The substrate holder can be rotated at high speed and is uniformly heated bya special resistive heater. In order to balance the thermal flow, N2 is introduced into thereactor uniformly from the upside. All above designs can reduce the pre-reaction of DEZn andO2 during the ZnO growth and uniform ZnO films may be grown by this MOCVD system.Furthermore, the plasma generator has been added to the MOCVD system in order to improvedoping efficiency during ZnO growth process and obtain high resistivity or p-type ZnO films. 3<WP=61>吉 林 大 学 硕 士 学 位 论 文 First, high-quality ZnO thin films have been grown on single-crystal Diamond substrateswith (111) orientation, by low-pressure metal–organic chemical vapour deposition. X-raydiffraction spectra and photoluminescence (PL) spectra clearly showed that the quality ofZnO films was improved by two-step growth method. Strong ultraviolet emissions and weakdeep-level emissions with different intensity were both observed in room-temperature PLspectrum. The change of surface morphology were also studied by atomic force microscopy(AFM). Raman scattering was performed at room temperature. The E2, A1(TO) and E1(TO)mode peaks were seen at 437.46, 383 and 414.87cm-1, which indicated a high crystallineintegrality of our samples. Piezoelectric ZnO layers with high resistivity for surface acoustic wave applicationshave been prepared on polycrystalline Diamond/Si substrates with (111) orientation byMetal-Organic Chemical Vapour Deposition. The characteristics of the films are optimizedthrough different growth methods. The comparative study of X-ray diffraction spectra andscanning electron microscopy shows that the final-prepared ZnO films had better c-axisconsistency. Zn and O elements in the final prepared ZnO films are investigated through x-rayphotoelectron spectroscopy, according to the statistical results, the Zn/O ratio is near 1.Raman scattering is also performed in back scattering configuration, E2 mode is observed infinal films, which is coincident with the group symmetry for the ZnO crystal structure.. Theresistivity of the films is also enhanced via the mo更多还原