蓝宝石衬底上原子级光滑AlN外延层的MOCVD生长

在蓝宝石衬底表面无氮化、低Ⅴ/Ⅲ比的情况下,采用1200℃的衬底温度、5kPa反应室气压,用MOCVD方法在蓝宝石衬底上生长出了表面原子级光滑的AlN外延层.原子力显微镜测试表明其平均粗糙度为0.44nm,X射线衍射(0002)回摆曲线FWHM为166".实验结果和分析表明,极性和气相反应是影响AlN表面形貌的主要原因.以原子级光滑的AlN为模板生长出了高质量的高Al组分的n型AlGaN,证实了AlN模板具有较好的质量.     

蓝宝石图形衬底上利用AlN缓冲层生长高质量GaN

在图形化衬底上以AlN作为缓冲层生长高质量的GaN薄膜,国内相关的报道较少。通过引入两步缓冲层生长方法,在蓝宝石图形衬底上生长基于AlN缓冲层的高质量GaN薄膜,利用低温AlN层生长时内部的缺陷,选择性进行腐蚀,形成衬底与外延层界面间的侧向倒斜角,提高光萃取效率;同时在其上继续生长高温AlN,为后续GaN薄膜提供高质量模板。从外延角度出发,以表面形貌及其上生长的GaN薄膜的晶体质量为衡量依据,优化了低温AlN缓冲层以及高温AlN缓冲层的生长参数,优化后LED样品在20 mA测试电流下的光输出功率较参考样品提升了4%。     

大面积规则排布的AlN纳米柱阵列制备

采用金属有机化合物化学气相沉积(MOCVD)方法在2英寸(1英寸=2.54 cm)c面蓝宝石衬底上异质外延厚度1μm、具有原子级平整表面的高质量氮化铝(AlN)外延层.并在此高质量AlN薄膜的基础上开发了基于纳米压印光刻技术、干法刻蚀和湿法腐蚀相结合的工艺,通过自上而下的方法制备得到了大面积范围内规则排列的AlN纳米柱阵列,纳米柱的高度和直径分别为1μm和535 nm.研究结果表明,高晶体质量的AlN材料以及基于AZ400K溶液的湿法腐蚀工艺是制备无腐蚀坑且侧壁光滑的垂直AlN纳米柱阵列的关键.AlN纳米柱阵列的制备为深紫外纳米柱发光器件的研究奠定了基础.     

应用厚缓冲层实现蓝宝石上高质量AlN外延层的MOCVD生长

在蓝宝石衬底上采用由低温AlN成核层、中温AlN生长层、温度渐变AlN生长层和高温AlN生长层组成的厚三维生长缓冲层来实现AlN外延层位错密度的减少和应力的释放.用光学显微镜、原子力显微镜(AFM)及X射线衍射仪对样品进行了表征,结果表明所生长外延层表面无裂纹,并显示出清晰的阶梯流表面形貌,其平均粗糙度为0.160 nm,KOH腐蚀坑密度为5.8×108 cm-2,(0002)和(10-12)回摆曲线FWHM分别为210”和396”.详细论述了AlN外延层的生长模式、位错行为和应力释放途径.     

高温形核层对蓝宝石衬底AlN薄膜质量的影响

采用两步生长模式的金属有机化学气相沉积方法在蓝宝石衬底上外延生长AlN薄膜,通过高分辨X射线衍射和原子力显微镜分析方法,研究发现蓝宝石衬底上外延生长的AlN薄膜晶体质量与高温AlN形核层的形核密度及晶粒大小密切相关,而形核密度决定于高温AlN形核层的初始铝体积流量,晶粒的大小取决于其厚度。优化了高温AlN形核层的初始铝体积流量和厚度等工艺参数。当高温AlN形核层的初始铝体积流量为30 cm3/min、生长时间为9 min时,高温AlN形核层的形核密度和晶粒大小最优,外延生长的AlN薄膜位错密度最低,表面最平整,晶体质量最好。     

蓝宝石衬底上HVPE-GaN厚膜生长

采用氢化物气相外延(HVPE)方法,以蓝宝石作衬底,分别在MOCVD-GaN模板和蓝宝石衬底上直接外延生长GaN.模板上的GaN生长表面平整、光亮,但开裂严重.其(0002)的双晶衍射半高宽最低为141″;蓝宝石衬底上直接生长GaN外延层质量较差,其双晶衍射半高宽为1688″,但不发生开裂.HCl的载气流量对预反应有很大的影响.应力产生于外延层和衬底之间的界面处,界面孔洞的存在可以释放应力,减少开裂.光致发光(PL)谱中氧杂质引起强黄光发射.     

蓝宝石衬底上HVPE-GaN厚膜生长

采用氢化物气相外延(HVPE)方法,以蓝宝石作衬底,分别在MOCVD-GaN模板和蓝宝石衬底上直接外延生长GaN.模板上的GaN生长表面平整、光亮,但开裂严重.其(0002)的双晶衍射半高宽最低为141″;蓝宝石衬底上直接生长GaN外延层质量较差,其双晶衍射半高宽为1688″,但不发生开裂.HCl的载气流量对预反应有很大的影响.应力产生于外延层和衬底之间的界面处,界面孔洞的存在可以释放应力,减少开裂.光致发光(PL)谱中氧杂质引起强黄光发射.     

通过双中温AlN插入层提高半极性(1122)面AlN薄膜的表面形貌和晶体质量

利用金属有机化学气相沉积方法在蓝宝石衬底上生长了一系列具有双中温AlN插入层(MTG-AlN)的半极性AlN薄膜样品。中温生长的AlN插入层具有较大的表面粗糙度,形成了类似纳米级图形化衬底结构,能够有效阻断高温生长的半极性AlN样品中堆垛层错的传播,从而提高半极性AlN样品的表面形貌和晶体质量。通过原子力显微镜和X射线衍射仪的表征,研究了MTG-AlN插入层厚度在20～100 nm之间的变化对半极性AlN样品的表面形貌和晶体质量的影响。结果表明,所有半极性AlN样品都具有■取向。当插入的MTG-AlN中间层厚度约为80 nm时,半极性AlN样品表面粗糙度显著降低,晶体质量明显改善。     

AlN缓冲层厚度对脉冲激光沉积技术生长的GaN薄膜性能的影响

在蓝宝石(Al2O3)衬底上应用脉冲激光沉积技术(PLD)生长不同厚度的AlN缓冲层后进行GaN薄膜外延生长。采用高分辨X射线衍射仪(HRXRD)和扫描电子显微镜(SEM)对外延生长所得GaN薄膜的晶体质量和表面形貌进行了表征。测试结果表明:相比直接在Al2O3衬底上生长的GaN薄膜,通过生长AlN缓冲层的GaN薄膜虽然晶体质量较差,但表面较平整;而且随着AlN缓冲层厚度的增加,GaN薄膜的晶体质量和表面平整度均逐渐提高。可见,AlN缓冲层厚度对在Al2O3衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响。     

AlN缓冲层厚度对脉冲激光沉积技术生长的GaN薄膜性能的影响

在蓝宝石(Al2O3)衬底上应用脉冲激光沉积技术(PLD)生长不同厚度的AlN缓冲层后进行GaN薄膜外延生长。采用高分辨X射线衍射仪(HRXRD)和扫描电子显微镜(SEM)对外延生长所得GaN薄膜的晶体质量和表面形貌进行了表征。测试结果表明: 相比直接在Al2O3衬底上生长的GaN薄膜, 通过生长AlN缓冲层的GaN薄膜虽然晶体质量较差, 但表面较平整; 而且随着AlN缓冲层厚度的增加, GaN薄膜的晶体质量和表面平整度均逐渐提高。可见, AlN缓冲层厚度对在Al2O3衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.