【作者】 王清涛；

【导师】 李清山；

【作者基本信息】 曲阜师范大学 ， 物理电子学， 2002， 硕士

【摘要】 因为单晶硅(Crystalline Silicon,c-Si)是间接带隙(E_g=1.1eV)材料，作为发光器件在光电子领域中的应用受到一定限制。虽然具有直接带隙的半导体化合物，如GaAs、InP等能有效发光，但它们价格昂贵、工艺复杂，且难以与现有的硅集成技术结合。1990年英国的Canham在室温下得到多孔硅(Porous Silicon,PS)高效率(〉1％)的可见光致发光，此后人们又相继实现了多孔硅多种颜色的光致发光(Photoluminescence,PL)和电致发光(Electroluminescence,EL)。多孔硅可能弥补单晶硅材料不能有效发光的缺点，预示了用单晶硅制备发光器件进而实现全硅光电子集成的美好前景。 本文用双池(two-cell approach)电化学阳极氧化法制备多孔硅样品。以应用为背景，从多孔硅的形成过程、发光性质和温度特性等方面作了较为详细的研究。第一章总结了前人的工作。第二章从多孔硅的形成机制入手，对多孔硅的微结构和光学性质进行了研究。认为在多孔硅形成的过程中，由于电荷转移，在Si／电解液界面处形成了一个电偶极层(ElectricDipole Layer)的同时，在硅片表面形成了一个空间电荷层(DepletionLayer)，它们对多孔硅的形成过程有重要影响。分析了氢氟酸浓度、电流密度、阳极氧化时间和光照条件等阳极化参数对多孔硅微结构和光学性质的影响，并在简要讨论了多孔硅的形成机理。我们认为，对n-Si来说，多孔硅的形成机制可概括为扩散限制模型更为合理，但量子限制在扩散过程中起着重要作用，对p-Si可概括为耗尽模型。 曲阜师范大学硕十研究生毕业论文 第4页 第三章研究了多孔硅在60－300K温度范围内的发光特性。结果表明， 多孔硅发光峰位随温度变化而移动的规律与其孔隙率有直接关系。随着温I 度的升高，高孔隙率多孔硅发光峰位红移，低孔隙率多孔硅发光峰位蓝移， 而一些中孔隙率多孔硅，其发光峰位基本不移动。并且还发现，多孔硅发 光强度随着温度的降低而增强，在中间温度达到最大值，继续降低温度其 发光强度则明显减弱。同时在分析其它大量实验现象的基础上，认为包围 纳米硅的界面氧化层p ＊参与了多孔硅发光。多孔硅至少存在两种发光 谱：量于限制发光谱和非量于限制发光谱，随着温度的变化，不同发光谱 对多孔硅发光的贡献不同，这就决定了多孔硅发光峰位、强度对温度的依 赖行为。提出并利用这种基于量于限制效应（oil川tllffi COnfillCttimt EffCCt， QCE）的综合发光模型解释很好地解释了实验结果。 第四章对多孔硅在一些领域内的实际应用的问题和前景作了展望。 至今，多孔硅的发光机制仍是存在争议的问题，但有两点基本达成了 共识：O）量子限制效应是基础；①表面态起着重要作用。要达成真正的共 识，还有待于更多理论及实验的论证、支持。更多还原

【Abstract】 The development of semiconductor photo-electronics has been dominated by III-V compound semiconductors such as GaAs and InP which are good at emitting light but are more expensive than silicon and are hard to integrate into silicon microchips, primarily due to the direct energy band gap available in many important III-V materials. In contrast, the development of Si-based photo-electronics has been severely limited by the fundamental band-structure limitation: a small and indirect band gap of 1.1 eV at room temperature. The observation of visible-light emission from porous Si has begun to revitalize silicon’s role as a material for optical electronics. The discovery that porous silicon (PS) can emit visible light at room temperature has aroused great interests because of its potential applications in the areas of optoelectronics and display system. However, the luminescence mechanism of PS is still a controversial problem.Electrochemical anodization method is the typical approach for preparing uniformly PS, which show intense PL in the visible wavelength region. The PS structure can be fabricated by simply anodizing bulk Si in an HF-based solution. The approach used in this paper is two-cell approach. Based on the applications in the future, this paper has in detail studied the formation mechanism, photoluminescence (PL) and temperature dependence of PL in porous silicon. After having summarized previous studies in chapter one, we present the research results for formation process and PL of PS in chapter two. The PS morphology and its optical properties strongly depend on the anodization parameters, such as anodization time, HF concentration,anodization current density, and illumination condition etc. the formation mechanisms of porous silicon are discussed at the same time. We believe porous silicon made of n-Si has different formation mechanism from that of p-Si.The temperature dependence measurement of the PL is generally considered as an important method to reveal the luminescence mechanism of PS. The property of PL from PS has been investigated in chapter three. It is found that the peaks from the high porosity samples show a red shift with increasing temperature, the peaks from the low porosity ones show a blue shift, others with moderate porosity are independent of temperature. And the emission intensity increases with decreasing temperature until reaching an intensity maximum at the intermediate temperature, and then decreases at lower temperature. Many experimental results which conflict with predictions of the quantum confinement model for PS luminescence have been analyzed at the same time. The SiOx layer covering the nanoscale silicon is believed to play an important role in PL of PS. PS has at least two kinds of different PL spectra in the nanoscale silicon and the SiOx layer. The reason why PL in PS is dependent upon temperature is that relative contributions to PL of the two PL spectra change with temperature. Finally, a new model based on quantum confinement effect is put forward to account for experimental facts as stated above.In chapter four this paper presents problems and expectation of porous silicon’s application in some fields in the future.更多还原