Fabrication, Optical and Electrical Properties of Selenium Micro-Nano Structures on Si Substrates

以Si材料为基础的微电子技术是当今信息化时代的关键支柱，已经达到相当成熟的产业化水平，在信息领域中做出了巨大的贡献。Si基化合物新材料在硅集成光电子和纳米器件如单电子器件、太阳电池以及薄膜晶体管等方面具有广阔的应用前景。然而，Si基化合物材料的发展相对比较缓慢，除SiGe材料外，其他Si基化合物材料的研究并不深入。因此，寻找新的性能优良的Si基化合物材料是进一步加快光电子集成发展的有效途径之一。本文利用超高真空气相沉积系统（UHVCVD）在Si基上制备了系列的Se微纳结构，研究其光电特性。取得以下主要结果： 在超高真空条件下，通过调控衬底的温度，在Si(100)表面制备出三种不同结构的Se薄...As the key mainstay of information age nowadays, microelectronic materials based on silicon have reached a mature industrial level, which make a great contribution to the field of information. As is well-known, Si-based materials posses a wide range of application such as single electron device, solar cell as well as thin film transistor. However, it is noted that the development of Si-based semic...学位：工学博士院系专业：物理与机电工程学院物理学系_微电子学与固体电子学学号：1982008015051

Analysis on The Ageing Mechanism of GaN-based Blue and Green LED by Electrical Stresses

对IngAn/gAn多量子阱蓝光和绿光lEd进行了室温20,40,60 MA加速电流下的电应力老化研究,发现蓝光与绿光样品经过60 MA电流老化424 H后,其电学性能表现出一定的共性与差异性:在小测量电流下,绿光样品的光衰减幅度较蓝光样品大~9%;而在较大测量电流(20 MA)下,两者的光衰减幅度基本相同(18%)。同时,蓝绿光样品的正向电学性能随老化时间的变化幅度基本一致,反映出它们具有相似的退化机制,绿光样品老化后增多的缺陷大部分体现为简单的漏电行为,而并非贡献于非辐射复合中心。在此基础上对gAn基外延结构进行了优化,优化后的lEd长期老化的光衰减幅度较参考样品降低了3%。The behavior of the related reliability of InGaN-based blue and green LED chips were investigated with 20,40,60 mA constant current stress up to 424 h at room temperature.Under 60mA constant current stress,the green LED chip showed more prominent optical power degradation at low measuring current levels than high measuring current levels.While,the blue LED chip showed the consistent optical power decrease at different measuring current levels.It should be pointed out that,at high measured current levels( 20 mA),blue and green LED chips expressed similar optical degradation( 18%) after the aging tests.Meanwhile,the aging stress does not significant affect the forward-bias electrical characteristics of blue and green LED chips,which indicated the similar degradation process in some aging tests.It is believed that the induced defects in blue LED by electrical stress mainly contribute to the nonradiative recombination centers,while in green LED chip the defects contribute to the localized leakage paths rather than the nonradiative recombination centers.Based on the mechanism analysis of blue and green LED,the design of GaN based epitaxial structure was optimized,and the thickness of quantum barrier was reduced to weaken the internal electrical field in the active layer to improve the reliability of LED.国家自然科学基金(61176050、61176092); 华侨大学科研基金(12BS226)资助项

Si( 100) 表面Se 薄膜生长及其在Ti /Si 欧姆接触中的应用

National Basic Research Program of China [2007CB613404]; National Natural Science Foundation of China [61036003, 60837001]; Natural Science Foundation of Fujian Province of China [2008J0221]We have investigated the growth of thin selenium layer on Si (100) substrate by molecular beam epitaxy (MBE). By controlling the temperatures of the silicon substrate and the selenium source during growth, an ultrathin film of Se is successfully grown on the Si(100) substrate. As the Si(100) surface is passivated by the ultrathin film of Se, the electrical property of the Ti/n-Si(100) contact is shown to be ideally ohmic, with low resistance and relatively high thermal stability

GaN基绿光LED芯片电流加速失效机理研究

采用电流加速的电应力老化方法研究GaN基绿光LED芯片的失效机理。LED芯片在经过60 mA电流老化424 h后,其发光效率总体趋势都是随老化时间增加而减小,但是小测量电流相比于大测量电流的发光效率衰减程度更为明显。同时,在正向偏压下电流电压曲线基本没有变化,而反向偏压下的反向电流随老化时间的增加而快速增加。笔者认为在电应力老化作用下,随老化时间增加,有源区的缺陷能级增多,在正向偏压下,缺陷能级起到一个有效陷阱的作用,增加了载流子的寿命,降低了辐射复合的几率,使得发光效率降低,但是并没有减小正向偏压下的电流,而反向偏压时,缺陷能级起到了一个漏电通道的作用,使得反向电流增大。福建省自然科学基金面上项目(2015J01655);;\n福建省教育厅基金项目(A类)(JA14025,JA13429)资助项

Se ultrathin film growth on Si(100) substrate and its application in Ti/n-Si(100) ohmic contact

本文采用分子束外延(MbE)系统在SI(100)表面淀积SE薄膜.通过控制衬底和固态SE束源炉的温度,实现了SE材料在SI(100)表面上的自限制超薄薄膜生长;在SE超薄层钝化的SI(100)表面上制备的TI金属电极具有低的欧姆接触电阻特性,且热稳定性温度提升至400℃.We have investigated the growth of thin selenium layer on Si (100) substrate by molecular beam epitaxy (MBE).By controlling the temperatures of the silicon substrate and the selenium source during growth, an ultrathin film of Se is successfully grown on the Si (100) substrate.As the Si (100) surface is passivated by the ultrathin film of Se, the electrical property of the Ti/n-Si (100) contact is shown to be ideally ohmic, with low resistance and relatively high thermal stability.国家重点基础研究发展计划(批准号:2007CB613404);国家自然科学基金(批准号:61036003和60837001);福建省自然科学基金(批准号:2008J0221);福建省教育厅科技项目(批准号:JB08215)资助的课题---

硅(100)衬底表面快速热退火制备硒纳米晶薄膜的结晶动力学

采用超高真空气相沉积系统在Si(100)衬底上制备非晶硒(Se)薄膜,然后快速热退火制得Se纳米晶薄膜。SEM观察结果表明,当热退火温度高于140℃,薄膜表面形貌从条状裂纹逐渐变成孤立的六角块状结构。Raman和XRD测试分析发现,退火后的Se纳米晶均为三角晶型结构,当退火温度高于140℃时,Se开始沿(100)方向择优取向结晶。分析得出,在Si(100)衬底上的Se晶粒(100)晶面的激活能比(101)晶面的激活能低,因而在(100)面上的结晶速率比(101)面上的结晶速率大,使得Se在(100)方向择优结晶。笔者认为这是因为Si(100)衬底对Se的结晶具有诱导作用,致使硒的结晶具有各向异性。福建省自然科学基金面上项目(2015J01655);;福建省教育厅基金项目(A类)(JA14025;JA13429);;华侨大学科研基金资助项目(12BS226

Photoluminescence properties of selenium nanocrystals on Si(100) substrate formed by rapid thermal annealing

由于尺寸缩小引起的量子效应,硒(SE)材料的低维纳米结构具有更高的光响应和低的阈值激射等特性,因此成为纳米电子与纳米光电子器件领域一个重要的研究方向.本文通过对非晶硒薄膜的快速热退火来制备硒纳米颗粒,退火温度在100—180 C之间时,结晶后的硒纳米颗粒均为三角晶体结构,其颗粒尺寸随退火温度的增加而线性增大.光致发光谱测试发现三个发光峰,分别位于1.4 EV,1.7 EV和1.83 EV.研究发现位于1.4 EV处的发光峰来源于非晶硒缺陷发光,位于1.83 EV处的发光峰来源于晶体硒的带带跃迁发光;而位于1.7 EV处的发光峰强度随激发功率增强而指数增大,且向短波长移动,该发光峰应该来源于非晶硒与硒纳米颗粒界面处的施主-受主对复合发光.We have investigated the structure and photoluminescence(PL) properties of Se nanocrystals(NCs) obtained by rapid thermal annealing of a-Se films on Si substrate.The size of Se NCs in a trigonal phase increases linearly with increasing temperature.Moreover,three PL peaks located at 1.4,1.7 and 1.83 eV are observed,which are attributed to the emission of defects in amorphous Se,donoracceprter pair(DAP) recombination at the interface of amorphous Se and Se NCs,and interband transition of Se crystals,respectively.华侨大学科研基金(批准号:12BS226); 福建省自然科学基金(批准号:2012J01277;2012J01284); 国家重点基础研究发展计划(批准号:2012CB933503); 国家自然科学基金(批准号:61036003;61176050;61176092;60837001); 福建省教育厅基金项目(A类)(批准号:JA12270)资助的课题~

A Dynamic Perception Coefficients Self-tuning Particle Swarm Optimization Algorithm Based on Nonlinear Systems

在优化非线性复杂系统问题中,智能算法已成为一种重要手段.提出了一种基于动态感知系数的自适应粒子群优化(particle swarm; optimization,PSO)算法(self-tuning; PSO,SPSO),将PSO算法的感知系数与神经网络算法结合,并于在线学习训练过程中动态调整感知系数,改善了PSO算法的计算效率以及全局收敛效率; .进一步将2个相互关联的神经网络比例积分微分(proportion integration; differentiation,PID)神经网络及SPSO神经网络结合起来,使其能有效解决非线性控制模型的问题.为了验证该算法,引入了4个仿真例; 及2种PSO优化算法传统PSO(conventional PSO,CPSO)和修正PSO(modified; PSO,MPSO),来比较SPSO算法在解决控制问题中的非线性复杂系统的高效性,结果显示SPSO算法有较好的全局收敛性能、收敛速度以及较强的鲁棒; 性.We propose a dynamic perception-coefficients algorithm,called; self-tuning particle swarm optimization (SPSO) in this paper, which is; used for determining optimal nonlinear systems.The theory of SPSO; integrates conventional PSO (CPSO) with neural network (NN) and trains; perception coefficients with the gradient descent algorithm to improve; computational efficiency,rate of convergence and global convergence.Then; we combine proportional-integral-derivative (PID) NN with SPSO to; optimize complex nonlinear systems.This paper presents four examples and; another two optimization algorithms CPSO modified PSO(MPSO) to help; estimate performances of the proposed SPSO.The result demonstrates that; the SPSO exhibits great performances in global convergence, rate of; convergence and strong robustness while optimizing complex nonlinear; systems.福建省科技计划项目; 泉州市科技计划项