利用FFT图象检测和分析砷化镓材料中的缺陷

砷化镓材料中缺陷的不均匀分布严重地限制了集成电路生产的重复性。本文首次提出一种利用傅里叶变换频谱图象检测和分析沿110和010方向上位错缺陷的统计分布的方法,称为FTIT检验法。文中定义的相参系数和纹理复杂系数是定量地检验制造集成电路材料中缺陷的重要指标。     

STUDY OF MORPHOLOGICAL DISTRIBUTION OF DEFECTS IN GaAs WAFERS BY INFRARED DIGITAL IMAGE PROCESSING

A new method is applied to characterize the defects in GaAs material(e.g.the absorption ofEL2 centres).The method consists of transmitting a laser beam(λ=1.1-1.5μm)through the GaAs wa-fer of 4—8 mm thickness and 50 mm diameter.The image is received by the TOSHIBA 8844 cameraand entered into the DATASUD computer image processing system.This image is displayed on amonitor permitting to observe the inhomogeneity(like cross,cells and volutes)of theEL2 and dislocation defects.This paper will introduce a specific image processing software for GaAs materi-al,called ZHIMAG(ZHang IMAGe)and its application to GaAs wafer.The software can bealso applied to any other types of image processing.     

Hydrogen passivation of defects and impurities in GaAs and InP

Hydrogen passivation experiments in GaAs and InP are discussed. For GaAs it is argued that the results of hydrogen passivation of shallow donors, shallow acceptors and deep centers in materials with different Fermi level positions as well as diffusion data for undoped or lightly doped GaAs are consistent with the assumption that hydrogen is neutral or amphoteric (at least at rather high temperatures of treatment). Some new interesting effects are reported such as improvement of GaAs homogeneity as revealed by microcathodoluminescence imaging and also hydrogen passivation of surface states in GaAs. Evidence is presented that hydrogenation in direct plasmas leads to damage region formation at the surface of the GaAs. A new method of hydrogenation is described that is free from that drawback. The marked improvement of Au/n-GaAs Schottky diodes I-V characteristics is reported after using this method. This new technique is also used to hydrogenate InP for which conventional methods encounter very serious problems. In InP the results of hydrogen passivation experiments on shallow donors and acceptors imply that hydrogen is a deep donor. An interesting effect of injection annealing at room temperature of hydrogen-donor complexes inn-InP is observed.     

GaAs体材料折射率红外椭圆偏振光谱研究

报道了采用红外椭圆偏振光谱术测量ＧａＡｓ体材料折射率,测量范围为２．５～１２．５μｍ,并将所得实验数据与理论计算和其它实验结果进行了对比,表明了实验结果的可靠性．     

采用图像分割方法进行木材表面缺陷的定量检测

随着木材加工业的集约化发展以及对木材表面加工质量高水平的苛求,传统的人工检测方式已经难以满足木材产品的加工生产。在了解木材表面缺陷的分类、缺陷产生原因和木材缺陷表面图像的特征的基础上,对比分析平均值法、最大值法和加权平均值法3种图像灰度化方法效果,并选定加权平均值法对木材缺陷图像进行灰度化预处理。在Matlab 6.5GUI编程框架下实现木材缺陷检测系统,通过选取Isodata聚类迭代法、Otsu最大方差法、最大熵法和Sobel边缘分割法为基础的4种阈值化图像分割方法对木材缺陷特征的分割效果和分割速率进行实验对比分析。实验结果表明,运用Isodata聚类迭代法的图像分割方法能够快速准确分割图像实现木材缺陷检测。     

FFT算法在电网谐波检测中的应用

影响数字信号处理发展的最主要因素之一就是处理速度。DFT使计算机处理频域信号成为可能,但当N很大时,直接计算N点DFT的计算量非常大。FFT可使DFT的运算量下降几个数量级,从而使数字信号处理的速度大大提高。本文介绍了如何利用高性能数字信号处理器实现FFT算法,给出了程序流程图及关键程序源码。该算法采用基2 FFT算法,参数计算主要采用查表法,计算量小,实时性高。在电网谐波检测应用中表明,该方法既能有效地检测出电网谐波,又能满足实时性要求。     

基于图像融合的木板表面缺陷检测研究

针对木板表面节子缺陷被染料染色后难以识别的问题,本文利用图像融合技术提出一种新的木板表面缺陷检测方法。该方法采集被染色木板的近红外图像和可见光图像,使用加权平均法、主成分分析（PCA）算法、小波变换、Laplacian金字塔变换等不同的融合算法对采集的近红外图像和可见光图像进行融合,然后对不同算法融合后的图像仔细观察分析和比对并计算其信息熵。实验结果证实,融合后的图像能够明显地辨别出染色后的木板缺陷,并且基于Laplacian金字塔算法的融合效果最好。     

Automated and calibrated whole wafer etch pit density measurements in GaAs

A technique for automated measurement of whole-wafer etch pit density (EPD) for GaAs wafers is presented. The technique relies on an infrared transmission experiment similar to that used to measure EL2 concentration. A theoretical relationship between transmission and EPD is established, including effects due to pit size. The new automated and old visual-count methods are compared on a 3“, low-pressure, liquid-encapsulated Czochralski wafer; it is established that the automated method has much better repeatability. An [EL2] map of this same wafer is also presented.     

MOCVD生长超突变结GaAs变容管材料

用ＭＯＣＶＤ生长了用于ＧａＡｓ变容二极管的结构材料。分别用ＳｉＨ＿４和ＣＣｌ＿４作为掺杂剂对ＧａＡｓ进行ｎ型和ｐ型掺杂，找到了适合高质量变容管材料的方法．材料用于器件制作，得到了反向击穿电压大于２５Ｖ、电容变化比大于４０的变容管。     

Novel Type of Wide-Bandwidth GaAs/AIGaAs Infrared Photodetectors

A novel asymmetrical GaAs/AlGaAs photoconductance infrared detector based on the new idea proposed in this paper has been developed,which uses the intersubband transition within the same conduction (valence) band due to infrared radiation. The detectors with two wells or six wells grown by Metalorganic Chemical Vapor Deposition (MOCVD) system are fabricated by etching a mesa size of 200tμm ×200μm. Evident infrared absorption on the wavelength from 5 to 10μm has been observed for two samples,so has the peak of negative differential conductance. It is demonstrated that the photocurrent together with the signal-to-noise ratio increases with the number of the wells, but have nothing to do with the increase of the noise current under the same electric field,i, e.,the voltage drops per period,as is different from the conventional GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIPs). The noise current is one order's magnitude lower than that of the conventional GaAs/AlGaAs QWIPs. It is anticipated that the photocurrent and detector performances can be improved further by increasing the number of wells and optimizing the structural parameters.     

砷化镓双栅场效应管及其在微波电路中的应用

本文简述砷化镓双栅场效应管的基本特性及其在放大器、倍频器.混频器、振荡器、移相器和开关等微波电路中的应用.     

FFT互相关算法在锅炉火焰双路检测中的研究

通过双路光学系统采集锅炉火焰点火信号,经光电转换、放大、滤波、ADC转换等预处理后,采用FFT互相关算法对两路探测信号进行互相关处理,发现该算法比时域相关算法具有判断精度高、抗干扰性能强等特点,进而优化了锅炉火焰检测信号处理算法,更适合用于实时监测锅炉内的火焰燃烧状况,为炉膛火焰安全燃烧提供了安全保障。     

LTE系统中混合基FFT算法分析与硬件实现

在LTE系统设计过程中,上行链路采用单载波频分多址技术(SC-FDMA),下行链路采用正交频分多址技术(OFDMA)。在用这两种技术实现LTE的过程中,都采用了DFT或FFT的处理方法,而直接计算DFT的计算量太大。因此本文通过对LTE系统中各种FFT算法进行了分析,重点对Cooley-Tukey FFT算法进行了研究,同时以变换区间N=12和N=15为例,通过电路复用的方式进行了FPGA实现与验证。     

基于FPGA的FFT算法优化及其在磁共振谱仪中的应用

提出了一种基于FPGA的依据核磁共振谱仪双通道频谱图对其信号增益和相位差不平衡进行调节的设计方案,详细阐述了FFT算法在FPGA中的设计与实现方法。该模块中的FFT处理器通过多个64点并行FFT模块复用实现,复数乘法全部采用移位相加来完成,大大降低了功耗,可移植性很强;并通过优化措施有效地降低了由于有限字长效应引入的噪声。结果表明,该设计大大提高了谱仪信号检测的准确性与使用的方便性。     

LTE物理上行共享信道中FFT算法分析与FPGA实现

快速傅里叶变换FFT作为数字信号处理的核心技术之一,使离散傅里叶变换的运算时间缩短了几个数量级,并在LTE中有重要的应用。现场可编程门阵列FPGA是近年来迅速发展起来的新型可编程器件。本文主要研究如何利用FPGA实现FFT算法,包括算法选取、算法验证、系统结构设计、FPGA实现和测试整个流程。设计采用Good-Thomas算法,利用Verilog HDL描述的方式实现了不定点FFT系统,并以FPGA芯片virtex4为硬件平台,进行了仿真、综合、板级验证等工作。仿真结果表明其计算结果达到了一定的精度,运算速度可以满足一般实时信号处理的要求。     

数字图像FFT算法及编程的探讨

随着计算机软件、硬件技术的迅速发展，离散傅里叶变换已经成为图像处理的一种重要手段。对于宽和高像素数为2的幂数的图像可以直接采用成熟的以2为基的FFT算法，而对于任意宽高的图像，它的FFT算法比较复杂。通过先采用插值算法对图像进行缩放，再进行基2的FFT变换，然后还原图像，实验表明，运算速度和结果都收到很好的效果。     

计算机图像处理与编程技术在检验中的应用

随着我国信息化社会的不断深入,社会各领域的发展也逐步向信息化、智能化方向迈进。图像处理作为当前信息处理的一个主要方法,在诸多领域都发挥着不可或缺的作用。本文主要以工业检验工作为例,在简要介绍计算机图像处理与编程技术的基础上,探讨上述2项技术在检验中的具体应用,从而将图像处理技术与编程技术的优势最大限度发挥出来,更好地推动国内工业产业的可持续发展。     

WSi_x薄膜及其与GaAs接触的特性

本文研究了用RF 溅射法形成之不同化学组份的WSi_x薄膜在退火前后的电阻率和内应力及WSi_x/n-GaAs肖特基接触的特性.结果表明:x的变化对薄膜及肖特基接触特性有严重影响,当x=0.62时.给出可耐800℃退火、具有高温稳定性的WSi_x/n-GaAs肖特基接触(φ_B=0.8eV,n=1.1),并在WSi_x栅自对准GaAs MESFET中取得了应用.     

Application of low temperature GaAs to GaAs/Si

Low Temperature grown GaAs (LT-GaAs) was incorporated as a buffer layer for GaAs on Si (GaAs/Si) and striking advantages of this structure were confirmed. The LT-GaAs layer showed high resistivity of 1.7 × 10⁷ ω-cm even on a highly defective GaAs/Si. GaAs/Si with the LT-GaAs buffer layers had smoother surfaces and showed much higher photoluminescence intensities than those without LT-GaAs. Schottky diodes fabricated on GaAs/Si with LT-GaAs showed a drastically reduced leakage current and an improved ideality factor. These results indicate that the LT-GaAs buffer layer is promising for future integrated circuits which utilize GaAs/Si substrates.     

射频集成电感器的快速傅立叶变换模拟及制备

应用磁像法和快速傅立叶变换（FFT）法对单片微波集成电路（MMIC）的薄膜平面射频集成电感器进行了电磁学模拟，并把模拟结果和有限元法（FEM）模拟的结果进行了比较。根据模拟结果，对薄膜平面射频集成电感器结构参数和加工参数进行了优化，改进了薄膜平面频集成电感器的工艺方案。最后结合薄膜平面射频集成电感器薄膜的高频损耗分析，讨论了平面薄膜集成电感器薄膜微细加工技术。