AlGaN中的应变状态

用X射线衍射和卢瑟福背散射方法研究了生长在GaN上厚度为570nm的AlxGa1-xN外延层中的应变状态.实验结果显示AlGaN的共格因子在组分小于0.42时随组分的增加而近似线性减小,并且在0.42时达到30%,此后随组分的增加变化较慢,在x=1(AlN)时接近0.在本实验条件中,由于GaN层处于压应变状态,导致与AlGaN外延层的失配变小,使得组分约为0.16的AlxGa1-xN外延层可以共格生长在GaN层上.     

AlGaN中的应变状态

用X射线衍射和卢瑟福背散射方法研究了生长在GaN上厚度为570nm的AlxGa1-xN外延层中的应变状态.实验结果显示AlGaN的共格因子在组分小于0.42时随组分的增加而近似线性减小,并且在0.42时达到30%,此后随组分的增加变化较慢,在x=1(AlN)时接近0.在本实验条件中,由于GaN层处于压应变状态,导致与AlGaN外延层的失配变小,使得组分约为0.16的AlxGa1-xN外延层可以共格生长在GaN层上.     

应变对AlxGa1-xN能带间隙弯曲系数和能带结构的影响

在生长AlxGa1-xN外延层过程中,由于外延层的热膨胀系数和晶格常数与衬底的不同,导致许多残留应变产生,这会影响外延层材料的能带结构和跃迁能.从理论上分析了在赝形应变下AlGaN的能带结构和弯曲系数,并通过对AlxGa1-xN能带间隙的理论结果和实验结果分析比较,得出的能带间隙的弯曲系数与已有文献报道的实验结果相吻合.     

AlGaN/GaN异质结单片集成紫外/红外双色探测器

采用分子束外延(MBE)技术在蓝宝石衬底上依次生长n+GaN下电极层、i型AlxGa1-xN势垒层和n+GaN发射极层,并通过半导体微细加工技术,制作了AlGaN/GaN异质结单片集成紫外/红外双色探测器。该器件利用不同的探测机理,同时实现了红外光和紫外光探测,拓展了响应光谱的范围。红外光探测是通过AlGaN/GaN异质结界面自由电子吸收和功函数内部光致发射效应完成的,紫外光探测是通过AlxGa1-xN势垒层带间吸收完成的。对单元器件的暗电流特性、紫外及红外光谱特性进行了测试。测试结果表明,紫外响应截止波长356 nm,响应度180 mA/W,红外响应峰值波长14.5μm,响应度49 mA/W。     

蓝宝石衬底上生长的铝镓氮外延膜的应变分析

采用金属有机化学气相沉积(MOCVD)方法制备了不同Al组分含量的2μm厚AlxGg1-xN外延膜,通过透射电镜定性分析了外延膜中的位错和缺陷,通过高分辨X射线衍射试验对AlxGa1-xN外延膜进行ω/2θ扫描,结果显示外延膜为六方晶系纤锌矿结构,通过对对称面和非对称面的晶面间距进行修正精确计算了外延膜晶格常数,并由此对应变进行定量分析,四个不同Al组分的AlxGa1-xN外延膜样品的四方畸变值随Al含量的增大而逐渐减小,并且均小于零,在水平方向上均处于压应变状态.     

基于MOCVD生长的高Al组分Al_xGa_(1-x)N的HRXRD研究

通过MOCVD设备,在c面蓝宝石衬底上异质外延了不同Al组分含量的Alx,Ga1-xN材料,生长过程中采用了低温缓冲层技术、脉冲原子外延技术(PALE)和多层超晶格缓冲技术,例如AlGaN/AlN SLs结构,成功得到了表面光滑无裂纹的AlxGa1-xN膜.并且通过HRXRD对材料进行了多个晶面方向上的摇摆曲线和20～ω表征测试,在此测试基础上时材料的Al组分、α轴和c轴的晶格常数以及位错密度进行了相应的计算,并定性的分析了材料的应变状态.     

MOCVD生长不同Al组分AlGaN薄膜

本文研究了利用金属有机物化学汽相淀积系统(MOCVD)生长高质量不同Al组分AlxGa1-xN薄膜(0.13＜x＜0.8).扫面电子显微镜(SEM)照片表明生长的AlN插入层有效地调节了AlGaN层与GaN支撑层的应力,使AlGaN表面平整无裂纹,原子力显微镜(AFM)测量得到所有AlGaN薄膜粗糙度均小于1 nm.通过原位干涉谱发现,AlGaN薄膜生长速率主要由Ga流量大小控制,随Al组分升高逐渐降低.利用X射线衍射和卢瑟福背散射(RBS)两种方法确定AlGaN薄膜的Al组分,发现Al组分与摩尔比TMAl/(TMGa+TMAl)关系为线性,说明在优化的生长条件下,Al原子与NH3的寄生反应得到了有效的抑制.     

高Al组分AlxGa1-xN薄膜的弹性-塑性力学性质

采用纳米压痕方法,研究了AlN/sphire模板上的高Al组分AlxGa1-xN薄膜的力学性质,特别是弹性-塑性转变行为.研究表明,AlxGa1-xN薄膜的杨氏模量E随着Al组分的增加而增大,薄膜中产生塑性形变所必要的剪切应力也随着Al组分的增加而增大.在AlxGa1-xN薄膜纳米压痕实验中,观察到位移不连续的跳断("pop-in")行为,并且发现"pop-in"行为强烈依赖于Al组分,Al组分的增加导致这种行为的减少.我们认为随着Al组分的增加,AlxGa1-xN中键能的增强和由于AlxGa1-xN与AlN/sapphire模板之间晶格失配减少这两个因素增加了AlxGa1-xN中新位错形成的阻力,从而导致了AlxGa1-xN薄膜中的"pop-in"行为随Al组分增加而减少.     

高Al组分AlxGa1-xN薄膜的弹性-塑性力学性质

采用纳米压痕方法,研究了AlN/sphire模板上的高Al组分AlxGa1-xN薄膜的力学性质,特别是弹性-塑性转变行为.研究表明,AlxGa1-xN薄膜的杨氏模量E随着Al组分的增加而增大,薄膜中产生塑性形变所必要的剪切应力也随着Al组分的增加而增大.在AlxGa1-xN薄膜纳米压痕实验中,观察到位移不连续的跳断("pop-in")行为,并且发现"pop-in"行为强烈依赖于Al组分,Al组分的增加导致这种行为的减少.我们认为随着Al组分的增加,AlxGa1-xN中键能的增强和由于AlxGa1-xN与AlN/sapphire模板之间晶格失配减少这两个因素增加了AlxGa1-xN中新位错形成的阻力,从而导致了AlxGa1-xN薄膜中的"pop-in"行为随Al组分增加而减少.     

AlGaN /GaN分布布拉格反射镜的MOCVD生长

文中利用MOCVD方法,采用高质量GaN作为缓冲层,在（0001）取向的蓝宝石衬底上实现了不同组分的AlxGa1-xN/GaN分布布拉格反射镜（DBR）的制备.通过XRD、SEM、AFM、反射谱等测量分析手段,研究了AlxGa1-xN/GaN DBR的结构质量、厚度和表面形貌.     

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.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks