【作者】 王如志；

【导师】 严辉； 王波；

【作者基本信息】 北京工业大学 ， 材料学， 2003， 博士

【摘要】 目前，III族氮化物半导体光电特性应用上研究上不断取得了令人振奋的突破。而III族氮化物半导体场发射研究作为其光电特性的重要研究方向，引起了人们广泛关注。本论文系统分析了目前场发射的研究现状、发展历史及应用前景，结合目前场发射研究所遭遇的困境。从理论与实验两方面研究了III族氮化物半导体薄膜具有优异场发射特性的物理实质，也就如何进一步改善其场发射性能提出了可能方法及思路。最后，基于自己对III族氮化物半导体薄膜场发射系统研究、分析与感悟，阐述了将来半导体薄膜场发射研究的可能发展方向。本论文的主要工作如下：1． 建立一用于研究宽带隙半导体薄膜场发射实质的能带弯曲理论模型。以III族氮化物半导体c-BN作为例，研究了宽带隙半导体具有场发射优异场发射实质，结果表明，对于宽带隙半导体优异的场发射特性，应该归功于外加电场导致的强能带弯曲及其NEA的共同作用，强能带弯曲提供发射电子源，而NEA使电子易于逸出表面势垒。修正了以前认为的宽带隙半导体的NEA特性是导致其优异场发射性能的主要因素的半导体场发射理论。此理论模型也取得了与实验一致的结果。 2． 基于能带理论建立起了纳米晶半导体场发射模型。应用纳米半导体场发射模型，分别理论地研究了III族氮化物半导体中的c-BN半导体薄膜场发射纳米增强效应及纳米AlxGa1-xN复合膜的热场发射特性，研究结果表明：小纳米晶粒半导体薄膜具有更为优异场发射特性；在不考虑纳米几何场增强情况下，半导体纳米场发射增强效应可能源于其NEA增强及带隙宽化后导致的强带弯曲；纳米AlxGa1-xN复合膜同样具有纳米场增强效应；纳米场增强效应大小也是与场发射体温度与合金成分指数密切相关的。3． 研究了工艺参数对不同相结构BN薄膜沉积的重要作用，发现基底温度及基底偏压在沉积高立方相结构BN薄膜中起着关键作用，其它工艺参数，如工作气压、沉积时间、气体浓度及采用缓冲层等在生长高质量BN薄膜的作用也是不可忽略的，但是其主要辅助提高及进一步改善质量；通过改变工艺参数，能基本控制BN相结构含量，同时也制备出立方相含量高达90%、粘附性良好的高质量1μm 以上的BN厚膜；通过研究不同相结构BN薄膜场发射性能，发现高立方相BN薄膜具有更为优异的场发射性能，除了不同相结构BN薄膜表面形貌引起的场增强外，场发射增强更主要的原因可能在于不同相结构薄膜键合方式不同而导致电子积累及表面势垒的异同，一般而言，sp3键合材料的场发射性能可能要优于<WP=4>4． sp2键合方式。5． 采用反应磁控溅射系统制备出了高取向蚕状晶AlN薄膜，研究了其取向机制，发现气压导致形核能及形核密度的改变可能是不同取向生长的关键因素。进一步研究了不同溅射参数对于AlN薄膜取向生长的影响，发现溅射功率密度、基底温度及基底材质也是影响取向生长的重要因素。6． 首次研究了取向半导体薄膜场发射机制。通过对不同取向的AlN薄膜场发射试验，发现单一取向的AlN薄膜具有较好场发射性能，而非单一取向薄膜在试验中没有测到场发射电流，这可能意味高取向对于薄膜场发射的作用是非常关键的。此外还研究了不同厚度的取向AlN薄膜的场发射性能，发现较薄AlN膜将利于场电子发射。更多还原

【Abstract】 III nitride semiconductors are currently experiencing the most exciting photoelectric characteristics development. As an important photoelectric exposure, field emission properties of III nitride semiconductors have attracted widely interestingness of researchers. In this thesis, considering the present embarrassment of field emission development, it analyze by the numbers the status, history and prospect of field emission from semiconductors. Then, the physical substance of excellent field emission performances of III nitride semiconductors were investigated both theoretically and experimentally, to more improve the field emission capability of semiconductors, it is also supplied some possible techniques and thoughts in this thesis. Finally, based on authors’ analysis and apperception, it shows the prospective research orientation of field emission from semiconductors. The main research work of this thesis as follow:1. A theoretical model based on the band bending theory was developed for explaining the field emission mechanism of wide-bandgap semiconductors (WBGSs). As an example of field emission from III nitride semiconductors, it analyzes the excellent field emission performance of cubic boron nitride (c-BN). The results draw a new thinking to explain the field emission mechanism, in which it is considered that the band bending, as well as the negative electron affinity (NEA), is of equal importance to the excellent field emission performances of WBGSs. In other words, the band bending contributes to supply enough quantities of effective electrons, and the NEA characteristic helps to free electrons from the surface potential. The calculated results are in agreement with the experiment data.2. An electron-emission theoretical model integrating the change in the grain size of nanocrystalline based on quantum theory was established. The nanocrystalline c-BN films field enhancement effect and nanocrystalline AlxGa1-xN composite films are researched theoretically. The results show that the emission current from nanocrystalline grain films is far larger than that from regular grain films or bulk. The field emission enhancement may originate from the NEA strengthen and the band bending increased because of the widen bandgap in nanocrystalline films. The nanocrystalline field emission enhancement is also close related with the composite index and emission temperature for AlxGa1-xN films. <WP=6>3. The important effects of deposited parameters to high quality BN film preparation are investigated. It shows that, the substrate temperature and the negative bias are two key factors, to improve the films performance, it is necessary to select suited other parameters, such as, deposition time, work pressure, nitrogen Concentration, buffer layers. The high quality BN with 90% cubic phase content, good adhesive and 1μm thickness is successfully deposited and the phase content of BN films can be controlled by changing the disposition parameter.4. Field emission properties from different cubic phase content BN films are studied, the results show there are better field emission performance from high cubic phase BN films than from low cubic phase BN films. Expect the geometry field enhancement, the enhancement effect of field emission from BN films with cubic phase content increasing is mainly rooted in the accumulated electron enhancing and the surface potential barrier lowing. Generally, there is bigger field emission current from sp3 bonding than sp2 bonding. 5. The high oriented gain silkworm-like AlN films are prepared by reactive magnetron sputtering It is found that nucleation energy and nucleation density caused by sputtering pressure is a key factor of high orientation films preparing. Furthermore, other sputtering parameters to the effect of AlN orientation growth are investigated, the results show that, power density, and wafer temperature and substrate are also the important parameters for the preferential orientation of AlN.6. Tropism mechanisms for field emission from semiconductor films a更多还原