论文标题:低温生长高质量氧化锌薄膜及其特性研究
The Growth of High Quality ZnO Thin Films at Low Temperature by PECVD & Study of Its Properties
论文作者 李炳生
论文导师 申德振；刘益春,论文学位 博士,论文专业 凝聚态物理
论文单位 中国科学院研究生院（长春光学精密机械与物理研究所）,点击次数 9,论文页数 94页File Size1877k
2002-05-01论文免费下载 http://paper.dic123.com/lunwen_106411897/ 氧化锌,等离子体增强的化学汽相沉积,X-射线衍射,光致发光,氮化作用,氮化锌,p-氧化锌
ZnO,PECVD,XRD,Photoluminescence,Nitridation,Zn3N2,p-ZnO.
由于紫外波段激光器在信息显示和信息存储特别是在海底探测，紫外通讯和光存储，医疗和诊断，防伪和检测，分析仪器等方面都有十分重要的应用，是一项具有重要应用前景的基础研究。氧化锌作为一种宽带隙半导体（3.3eV），激子束缚能大（60meV），在室温下容易获得强的激子发射，而且可能成为紫外激光的重要材料。因此，对氧化锌的研究已成为继GaN之后宽带隙半导体研究的又一热点。为了获得高质量的氧化锌薄膜材料，人们已采用分子束外延，有机化学汽相沉积，脉冲激光沉积，磁控溅射等各种技术来制备氧化锌薄膜材料。为了在低温下制备高质量的氧化锌薄膜，我们采用金属有机源和二氧化碳气源，首次利用等离子体增强化学气相沉积的技术在低温下制备了高质量的氧化锌薄膜，系统地研究了生长条件以及衬底表面氧化层对薄膜质量的影响，确定了生长高质量氧化锌薄膜的优化条件；为获得p-ZnO材料，克服在ZnO中掺N杂质间相互作用影响掺杂效率不易获得p-ZnO的困难，我们通过热氧化Zn3N2的方法制备了p-ZnO，获得了一系列研究结果：1、详细研究了气体流速比，衬底温度和射频功率实验参数对氧化锌薄膜特性的影响。首次报道了用这种方法在衬底温度为180 oC条件下制备了（0002）择优取向，其X-射线衍射峰的半峰宽为0.2度的高质量氧化锌薄膜。2、详细研究了氧化锌薄膜的光学特性，分析了氧化锌薄膜光学特性和发光特性与制备条件的关系。在高质量氧化锌薄膜中室温下观察到了强的激子吸收，在发光谱中，得到了半高宽为90meV的强的自由激子发射。3、首次报道了射频功率对氧化锌薄膜性质的影响。随着射频功率从6 W增大到19W，氧化锌薄膜的结晶性逐渐增强，当射频功率为19W时，氧化锌具有强和窄线宽的自由激子发射，薄膜表面平整，晶粒均匀。然而随着射频功率的进一步增加，薄膜的结晶质量降低，紫外发光变弱，深缺陷发光增强，薄膜的表面平整度变差。4、通过用等离子体对硅衬底表面进行清洗和钝化两步处理，解决硅衬底表面的氧化层和界面电荷平衡问题，制备出了高质量的氧化锌薄膜材料，找到了一条获得了高质量的氧化锌薄膜的新途径。5、用等离子体增强的化学汽相沉积的方法制备了Zn3N2 薄膜，首次通过热氧化Zn3N2的方法，制备出了受主型载流子浓度为1017cm-3的p-ZnO薄膜。通过这种方法可以克服N原子不容易惨杂进氧化锌的困难，并且可以通过控制退火过程来控制N原子的掺杂浓度。为制备p-ZnO提供了一种新的思路和方法。
Recently much attention has been paid to short wavelength lasers for use in high density information storage, information display, UV communication, medical treament & diagnisis, and so on, which make it become an important basal research with extensive application. It is widely accepted that ZnO is one of the most promising materials for producing an ultraviolet laser at room temperature due to its wide direct band gap (Eg=3.3eV) and large excitonic binding energy of 60 meV, which was testified by the results of optically pumped stimulated emission and lasing from ZnO thin films. Like GaN compound, the reasearch about ZnO has burned white hot in the range of wide band gap.To study its properties and obtain high quality thin films, a variety of techniques have been used such as molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), magnetron sputtering, pulsed laser deposition, to prepare ZnO thin films. In order to otain high quality ZnO thin films, we, for the first time, employ the plasma enhanced chemical vapor deposition (PECVD) to prepare high quality ZnO thin film at low temperature using a zinc organic source (Zn(C2H5)2) and carbon dioxide (CO2) gas mixtures. The effects of the growing condiction and the native oxide layer of Si substrate on the quality of ZnO thin films was studied in detail. To prepare p-ZnO and overcome the dufficulty of reverse due to the interaction between the N atomic, we obtain high qulaity p-ZnO by a easy way of thermal Zn3N2. The major results lists as following:1 The relationships between the substrate temperature, the gas flow ratio of Zn(C2H5)2 to CO2, and the rf power and the properties of ZnO films are studied in detail. For the first time,we obtain a (002) orientated high quality ZnO thin films with the full width at half maximum (FWHM) of 0.2o located at 34.42o at a low temperature of 180℃.2 The optical properties of ZnO prepared by the PECVD are studied in detail. The relationship between the optical characteristic of ZnO and the preparing condition is studied. A strong excitonic effect on ZnO thin films at room temperature is observed in optical absorption spectra. An excellent free exciton emission with a narrow FWHM of 90 meV is obtained. 3 For the first time, the effects of rf power on the properties of ZnO are studied. With an increase of inputting rf power (6-19 W), the crystal quality of ZnO thin film is improved, however, a further increasing rf power, the crystal quality become poor. The ZnO thin film prepared at rf power of 19 W shows an excellent optical character identified by photoluminescence, a smooth suface testified by AFM. With increasing the inputting rf power further, the intensity of visible band emission increase, on the contrary, the intensity of UV band decreas. The surface also becomes rough as further increasing rf power.4 The cleanout and the passivation of Si surface was carried out by a two-step process to overcome the surface oxide layer and balance the charge between the substrate and epitaxy. By this way, the crystal quality and emission characteristic of ZnO thin films can be improved, which provide a way to resolve the native oxide layer of Si substrate. 6 The Zn3N2 is prepared on focus glass substrate at low temperature. And for the first time, a p-ZnO with a carrier density of 1017?cm-3 is obtained by thermal Zn3N2 in an oxygen ambient. The difficulty can be overcomed that the N atom is not easy to be doped into ZnO. If we control the annealing condition, the residual nitrogen atoms will become acceptors in ZnO:N films. As a result, we can obtain P-type ZnO thin films with a high carrier density. density. Success in realizing p-type ZnO in an easy way will undoubtedly widen the range of application for ZnO in a great extent.
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