硅量子点在异质界面能带调控和电荷存储中的应用研究

发布时间：2018-03-17 07:24

  本文选题：硅量子点　切入点：异质结　出处：《华中科技大学》2016年博士论文　论文类型：学位论文

【摘要】：硅量子点材料因具有独特的量子效应被广泛应用于光电子和微电子器件中,文中阐述了采用等离子增强化学气相沉积和热退火工艺制备硅量子点的工艺流程,并对不同退火条件下制备的富硅SiC:H薄膜进行了表征分析,证明了退火处理后样品中硅量子点的存在。制备了Si-rich a-SiC:H/c-Si异质结构,通过改变退火条件,研究了Si-rich a-SiC:H薄膜中微结构演变与Si-rich a-SiC:H/c-Si异质界面能带分布之间的关系,实现了对Si-rich a-SiC:H/c-Si异质界面能带带阶的调整。Si-rich a-SiC:H/c-Si异质界面的能带分布主要受薄膜中量子点结晶度、量子点尺寸和Si与SiC量子点比例等因素的影响,异质界面能带调控有助于改善载流子的界面传输特性和提高异质结器件的性能。为探索硅量子点材料在异质界面能带调控中的应用前景,通过模拟仿真研究了硅基异质结太阳能电池界面能带分布对界面传输性能的影响。经过对硅基异质结界面能带的分析,最终获得硅基异质结太阳能电池的光电转换效率为27.37%(开路电压为805.5 mV,短路电流密度为41.85 mA/cm2,填充因子为81.2%)。另外,以采用MOCVD工艺制备的掺硼ZnO(BZO)薄膜作为透明电极制备了硅基异质结太阳能电池,研究了B2H6流量和衬底温度对BZO薄膜微结构、光学和电学性能的影响；当B2H6流量约为10 sccm和村底温度约为170℃时,优化得到的BZO薄膜的电学参数范围为：电阻率为9.0～1.0×10-3 Ω cm,电子迁移率为16.5-25.5 cm2/Vs,载流子浓度为2.2～2.7×1020cm-3。将优化后的BZO薄膜用于硅基异质结太阳能电池,并与以ITO透明导电薄膜作为透明电极的异质结太阳能电池进行了对比分析,发现,以BZO薄膜作为透明电极的太阳能电池的η为17.788%,Voc为0.628 V,Jsc为41.756 mA/cm2,填充因子为0.678；以ITO薄膜作为硅基异质结太阳能电池的的η为16.443%,Voc为0.590 V, Jsc为36.515 mA/cm2,填充因子为0.762,以BZO薄膜作为前后透明电极的硅基太阳电池比以ITO作为透明电极的太阳能电池具有更好的光电转换性能。在电荷存储器方面,以含Si量子点的a-SiC:H薄膜为电荷存储层制备了电容存储器,研究了它的充放电过程和机制。首先,以不同扫描电压下的C-V特征曲线验证了Si量子点的电荷存储行为；通过G-V曲线中电导峰的移动分析了电容存储器件中电荷在衬底和Si量子点间的转移过程。分析表明,电荷存储层中的大多数Si量子点的库伦充电能大于室温下电子的热能,Si量子点具有库伦阻塞效应；较大尺寸的Si量子点具有更小的库伦充电能,能够俘获两个或者更多的电子；Si量子点的充放电取决于Si量子点与a-SiC:H基质间的势垒以及Si量子点的尺寸和量子点间的距离,较大尺寸的Si量子点和较低的势垒能增强Si量子点的电荷存储效应,即增大存储器的存储窗口。
[Abstract]:Silicon quantum dots are widely used in photoelectron and microelectronic devices because of their unique quantum effects. The process of preparing silicon quantum dots by plasma enhanced chemical vapor deposition and thermal annealing is described in this paper. The Si rich SiC:H films prepared under different annealing conditions were characterized and analyzed. The existence of silicon quantum dots in the annealed samples was proved. The Si-rich a-SiC: h / c Si heterostructure was prepared by changing the annealing conditions. The relationship between the microstructure evolution in Si-rich a-sic: h thin film and the energy band distribution at the Si-rich a-sic: h / c-Si heterointerface is studied. The adjustment of the band order of the Si-rich a-SiC: h / c-Si heterointerface is realized. The energy band distribution at the Si-rich a-SiC: h / c Si heterointerface is mainly due to the crystallinity of the quantum dots in the film. The effects of the size of quantum dots and the ratio of Si to SiC quantum dots, The heterojunction band regulation can improve the interfacial transport characteristics of carriers and the performance of heterojunction devices. In order to explore the application prospect of silicon quantum dots in heterojunction energy band regulation, The influence of the energy band distribution at the interface of silicon based heterojunction solar cells on the interfacial transport performance is studied by simulation. Finally, the photoelectric conversion efficiency of the silicon based heterojunction solar cells is 27.377.In addition, the open circuit voltage is 805.5 MV, the short-circuit current density is 41.85 Ma / cm ~ 2, and the filling factor is 81.2%. Si-based heterojunction solar cells were prepared by using boron doped ZnO- BZO thin films prepared by MOCVD process as transparent electrode. The effects of B _ 2H _ 6 flow rate and substrate temperature on the microstructure, optical and electrical properties of BZO thin films were investigated. When the flow rate of B2H6 is about 10 sccm and the bottom temperature is about 170 鈩，

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