Optimizing Structure and Processes of Nickel Induced Lateral Crystallization

The structure and processes of nickel induced lateral crystallization are studied.The structure of metal induced lateral crystallization(MILC) is improved by opening a seed window on the buried oxide,which is helpfu to get superior quality of large grain poly Si at low temperature.By optimizing the temperature and time of annealing based on others' pervious work,the large grain poly Si with few defects are obtained,and the typical grain size is 70～80μm.The methods of etching NiSi 2 which is created after the long time annealing are also studied for the first time.Finally,a method is successfully chosen to reduce the possible contamination of Ni and to guarantee the MILC for the submicron VLSI application.

Influence of High Temperature Treatment on the Performance of Nickel-Induced Laterally Crystallized Thin Film Transistors

Well known for their good performance,thin film transistors (TFTs) with active layers which were nickel induced laterally crystallized,are fabricated by conventional process of dual gate CMOS.The influence of pre high temperature treatment of device fabrication on the performance of TFTs is also investigated.The experiment shows that the high temperature treatment affects the performance of the devices strongly.The best performance is obtained by adopting pre treatment of 1000℃.The mobility of 314cm 2/(V·s) is obtained at NMOS TFTs with pre treatment of 1000℃,which is 10% and 22% higher than that treated at 1100℃ and without pre high temperature treatment,respectively.A maximum on/off current ratio of 3×10 8 is also obtained at 1000℃.Further investigation of uniformity verifies that the result is reliable.

Lateral stress-induced propagation characteristics in photonic crystal fibres

Using the finite element method, this paper investigates lateral stress-induced propagation characteristics in a photonic crystal fibre of hexagonal symmetry. The results of simulation show the strong stress dependence of effective index of the fundamental guided mode, phase modal birefringence and confinement loss. It also finds that the contribution of the geometrical effect that is related only to deformation of the photonic crystal fibre and the stress-related contribution to phase modal birefringence and confinement loss are entirely different. Furthermore, polarization-dependent stress sensitivity of confinement loss is proposed in this paper.

Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

Polycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.

Crystallization of amorphous silicon beyond the crystallized polycrystalline silicon region induced by metal nickel

Crystallization of amorphous silicon（a-Si） which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization（MIC） polycrystalline silicon（poly-Si） regions is observed. The crystallization is found to be related to the distance between the neighboring nickel-introducing MIC windows. Trace nickel that diffuses from the MIC window into the a-Si matrix during the MIC heat-treatment is experimentally discovered, which is responsible for the crystallization of the a-Si beyond the MIC front. A minimum diffusion coefficient of 1.84×10^-9cm^2/s at 550℃ is estimated for the trace nickel diffusion in a-Si.

氨热法GaN单晶生长的位错密度演变研究

氮化镓单晶具有高击穿电压、直接带隙、高饱和电子漂移速率、良好的化学稳定性等特性,在光电子器件和大功率电子器件中有广泛的应用。然而异质外延氮化镓会产生高位错密度,限制了氮化镓基器件的性能发挥。本研究以HVPE-GaN为籽晶,采用氨热法生长了氮化镓单晶,利用扫描电子显微镜(SEM),光学显微镜和湿法腐蚀研究了氨热法氮化镓单晶籽晶区至侧向生长区的位错演变。研究结果表明,侧向生长区的氮化镓单晶位错密度明显低于籽晶区,侧向生长超过25μm后,位错密度降低2个数量级。

SiC功率LDMOS器件发展现状及新进展

集成化和小型化是未来电力电子技术的发展方向,SiC-横向扩散金属氧化物半导体(LDMOS)器件兼有SiC材料优势和LDMOS器件优势,击穿电压高、比导通电阻低、易与其他器件集成,在单片功率集成和小型化应用中起着重要的作用,但受限于晶圆材料和部分工艺加工技术而发展有限。综述了国内外SiC晶圆材料和SiC-LDMOS器件结构的发展现状,着重从衬底材料、晶体取向和器件结构优化方面阐述了SiC-LDMOS的研究进展,指出了SiC-LDMOS全面发展的瓶颈所在,展望了未来SiC-LDMOS的发展方向。

拓扑绝缘体与函数型光子晶体分界面上的Goos-Hänchen位移调控

运用传输矩阵法和固定相位法研究拓扑绝缘体与SINC函数型光子晶体分界面上的Goos-Hänchen效应。结果表明,两种线极化波在分界面处的Goos-Hänchen位移随入射角、拓扑绝缘体的介电常数、函数光子晶体周期数不同而呈现不一样的规律。可以通过调节入射线极化波的入射角、改变函数光子晶体周期数或在表面涂覆不同的拓扑绝缘体来控制分界面上的Goos-Hänchen位移。

Crystallographic tilt in GaN lavers grown by epitaxial lateral overgrowth

The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) onsapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). Itwas found that ELO GaN stripes bent towards the SiNx mask in the direction perpendicular toseeding lines. Each side of GaN (0002) peak in DC-XRD rocking curves was a broad peak relatedwith the crystallographic tilt. This broad peak split into two peaks (denoted as A and B), and peak Bdisappeared gradually when the mask began to be removed by selective etching. Only narrowpeak A remained when the SiNx mask was removed completely. A model based on these resultshas been developed to show that there are two factors responsible for the crystallographic tilt: Oneis the non-uniformity elastic deformation caused by the interphase force between the ELO GaNlayer and the SiNx mask. The other is the plastic deformation, which is attributed to the change ofthe threading dislocations (TDs) from vertical in the window regions to the lateral in the regionsover the mask.

高聚物结晶后期动力学过程的研究进展

回顾了描述高聚物结晶后期动力学过程的各种模型、方程以及数据处理方法 。

优质大尺寸Nd∶YAG晶体生长技术的研究

本文研究了Ｎｄ：ＹＡＧ晶体由于小面的生长而产生核心与侧心的机理。讨论了熔体生长Ｎｄ：ＹＡＧ晶体的固液界面形状和温度梯度及小面生长的内在联系；探讨了消除侧心、减小核心的技术途径；并生长出无侧心、小核心Ｎｄ：ＹＡＧ晶体。

液晶瞬态技术测量带侧向流扰流柱通道端壁换热

采用热色液晶瞬态测量技术测量带侧向流扰流柱通道端壁全表面换热系数的分布，研究了侧流比及雷诺数对换热的影响，其中，侧流比为0．25～1．0，雷诺数为3×10^4～9×10^4。结果表明：（1）侧流比对扰流柱通道的流动形态及端壁换热有重要影响；（2）存在一个临界侧流比，在临界侧流比以下，流动形态沿主流方向呈错排流状态；在临界侧流比以上，流动形态沿侧流方向呈错排流状态；在临界侧流比附近，流动为顺排流动状态，方向在主流和侧流方向之间；（3）侧流比较小或较大时，扰流柱通道端壁换热较强；在临界侧流比附近，换热相对较弱。

光子晶体调制半导体激光器侧模

为了实现半导体激光器的单侧模稳定工作,提出了一种在激光器的脊条两侧引入光子晶体结构滤除半导体激光器高阶侧模的方法。通过调整激光器上表面的刻蚀深度、光子晶体区域的条宽和间隔来改变激光器内部的模场分布,同时结合选择性的载流子注入来增强基模的激射优势,进而减少侧模的数量。实验上制作了主脊条宽度为6μm,光子晶体周期5μm,波长1 550 nm的半导体激光器。测试结果表明:在连续工作的情况下,电流300 mA的时候,高阶侧模受到抑制,水平发散角变为10.2°,证实了光子晶体结构调制激光器侧模的可行性。

超低阈值横向腔光子晶体面发射激光器

首次在无DBR结构的商业外延波导晶片上实现了电泵横向腔光子晶体面发射激光器(LC-PCSEL)。深孔刻蚀技术使光子晶体深达2.6μm,穿透有源区,对有源区的模式直接调制。通过较小区域的光子晶体与FP腔的融合集成,利用带边模式Γ2-1的横向振荡垂直输出特性,室温下获得了1553.8 nm的面发射激光,线宽0.4 nm。超低阈值电流密度为667 A/cm2,纵向和横向的远场发散角分别为7.5°和5.5°。LC-PCSEL的设计为电注入面发射激光器的研制提供了新的思路,为该类激光器的批量生产提供了可能。

基于二维声子晶体的大尺寸夹心式换能器的优化设计

夹心式换能器应用极为广泛,但当其横向尺寸过大时,存在耦合振动,影响其辐射面的位移分布.本文通过在大尺寸夹心式换能器的前盖板中加工周期排列的槽,来形成一种二维声子晶体结构.随后,采用有限元法对基于二维声子晶体的大尺寸夹心式换能器的振动传输特性、共振频率以及发射电压响应进行仿真模拟,讨论了开槽高度和开槽宽度对其带隙、共振与反共振频率、带宽以及辐射面位移分布的影响.研究结果表明,通过在大尺寸夹心式换能器中应用声子晶体结构可对其进行优化设计.当大尺寸夹心式换能器的工作频率位于其带隙范围内时,二维声子晶体结构能有效地抑制其横向振动,从而改善换能器辐射面位移分布的均匀程度.此外,在大尺寸夹心式换能器的前盖板中加工二维声子晶体结构,能有效提升换能器的带宽,进而拓宽大尺寸夹心式换能器的工作频带.

电场增强金属Al和Ni诱导非晶硅横向结晶

本文分析了Al和Ni在外加电场作用下诱导非晶硅(a-Si)薄膜横向结晶的特点和机理。对影响非晶硅结晶的诸多因素,如场强、金属种类和退火条件进行了研究。简要概述了金属诱导横向结晶(MILC)相对于其它一些结晶工艺的优势及其在薄膜晶体管(TFT)中的应用。指出适当强度的电场可显著加快横向诱导结晶的速率,但场强超过一临界值后,则降低该速率,并基于电迁移效应较合理地解释了该现象。

高性能金属诱导单向横向晶化多晶硅薄膜晶体管技术和应用

低温金属单向诱导横向晶化多晶硅薄膜晶体管技术与常规的固相晶化多晶硅薄膜晶体管相比 ,制作工艺简单 ,而且提高了场效应迁移率和漏极击穿电压 ,降低了漏电电流 ,改进了器件参数空间分布的均匀性。我们使用金属单向诱导横向晶化多晶硅薄膜晶体管技术 ,成功地制作了有源矩阵液晶显示器和有源矩阵有机发光二极管显示器。

金属诱导非晶硅横向晶化形成的多晶硅的生长研究

详细研究了金属诱导非晶硅横向晶化时间、温度对晶化生长的影响。结果显示 ,晶化生长速度受温度影响较大 ,其最大生长速度在 6 2 5℃附近。在较高的温度下 ,非晶自发成核和晶化 ,从而限制了金属诱导晶体生长速度。镍诱导源的长度和厚度也对晶体生长有影响 。

基于二维声子晶体结构的大尺寸超声塑料焊接系统

在大尺寸的圆柱形超声塑料焊接系统的工具头上加工周期性槽,形成一种二维声子晶体结构。对基于二维声子晶体结构的圆柱形工具头进行了声子晶体的带隙分析,并对优化设计后的该超声塑料焊接系统进行数值模拟。探讨了开槽前后超声塑料焊接系统振型的变化以及工具头输出端面纵振动的位移分布。研究结果表明,二维声子晶体结构能有效地抑制横向振动,增强纵向振动,并均匀输出端面的振幅,可以实现对超声塑料焊接系统的优化设计。

基于光子晶体的一维位置敏感探测器

位置敏感探测器(PSD)是基于半导体的横向光电效应的光电转换器件。根据横向光电效应的原理,增强光生载流子的寿命可提高光生载流子的扩散长度,从而实现横向光电效应的增强。利用缺陷和完整光子晶体设计了一维位置敏感探测器,并用传输矩阵法计算了缺陷光子晶体的透射率和完整光子晶体的反射率。从所设计的位置敏感探测器对入射光的响应理论研究表明,提高缺陷光子晶体的透射率和完整光子晶体的反射率可提高光生载流子的寿命,从而实现增强位置敏感探测器的横向光电效应。