Microwave switching with parallel-resonated GaAs FETS

The use of GaAs FETs as microwave switches is discussed, and the feasibility of such devices for applications requiring ultra low dc power consumption, low insertion loss, and bidirectionality is demonstrated. A discrete SPST switch consisting of two parallel-resonated single-gate GaAs FETs exhibited 0.5 db insertion loss with 25 db isolation at 8.5 GHz. The first monolithic SPDT switch incorporating parallel-resonated GaAs FETs is also reported.     

Automatic pattern positioning of scanning electron beam exposure

When making a pattern for a solid-state device from a silicon wafer coated with photoresist by the scanning electron beam exposure technique, the positioning accuracy of the pattern is as important as its resolution and dimensional accuracy. A pattern positioning system automated by an electronic computer which is included in the electron beam exposure apparatus type JEBX-2B, is introduced and described. Information conveyed by backscattered electrons from the wafer surface is utilized as a signal which detects the wafer locus and automatically corrects any x-, y-directional and rotational errors. It is shown that the positioning accuracy is within 0.5 µm. It can be improved under some limited conditions.     

Planar Be-implanted GaAs junction formation using swept-line electron beam annealing

Comparative studies of swept-line electron beam annealing and furnace annealing of Be implanted in n-GaAs doped with Si are presented. Electron beam annealing causes less Be redistribution and results in fewer traps than furnace annealing, but causes site mixing Of amphoteric Si. Planar Be-implanted junctions result in a p⁺-v-n structure for the electron beam annealed samples, similar to thermally quenched samples. We believe that this is caused by the incorporation of amphoteric Si on Ga and As sites during transient annealing, which produces results similar to thermal quenching.     

Etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning

The thermochemical etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning has been studied. The etch rate changes between GaAs and AlGaAs epilayers as the etching process proceeds through the layered sample. The phenomenon can be explained by the difference of thermal parameters of the heterojunction interface. The local temperature rise from laser irradiation has been calculated to investigate etching characteristics for GaAs and AlGaAs. It is concluded that the good thermal confinement at GaAs/AlGaAs interface produces the wider etch width of GaAs layer than that of AlGaAs layer in GaAs/AlGaAs multilayer. The maximum etch rate of the GaAs/AlGaAs multilayer was 32.5 μm/sec and the maximum etched width ratio of GaAs to AlGaAs was 1.7.     

Measurement of minority carrier lifetime in GaAs and GaAs1−xPx with an intensity-modulated electron beam

A new method of measuring short minority carrier lifetimes with a Scanning Electron Microscope (SEM) is reported. Main features are high spatial resolution (3 ωm in GaAs at 30 keV energy of beam electrons) and the insensitivity to surface recombination by use of a Schottky-contact. The shortest measurable lifetime is approx. 100 ps depending on sample conditions.The minority carrier lifetime is evaluated from the phase rotation between the measured ac-EBIC and the ac-component of the intensity modulated electron beam. The diffusion length required for the analysis is measured by the collection efficiency of the Schottky-contact, similar to the method of Wu and Wittry. Application of the method is demonstrated with a GaAs sample and a GaAs_1?xP_x sample. EBIC micrographs (phase and amplitude) show local flucuations of lifetime and diffusion length.     

基于PCI-1721电子束磁扫描焊接的软件设计

基于高速模拟量输出板卡PCI-1721,运用Delphi 2007设计开发了电子束扫描路径的编程焊接软件.该软件仿照CNC的G指令,编辑电子束扫描路径代码,通过G代码进行电子束磁扫描焊接,避免了进行电子束磁扫描焊接时,不同焊缝曲线需要编写不同软件的弊端.应用分析表明,该软件通过G指令编程能够进行平面焊缝曲线的电子束磁扫描焊接.     

Laser mechanism in the excitation of plasma oscillations by an incident electron beam

It has been shown that intense plasma oscillation could be excited through the coupling of two charged fluids with high relative velocities. Both classical and quantum mechanical treatment of the problem lead to the same conclusion, all giving a picture of a laser process in the exponential increment of the amplitudes of oscillations. Direct insight is afforded by the quantum mechanical treatment in that the self-stimulation of the modes of oscillation plays the essential role in the amplification. The appearance of a complex frequency in the solution of the secular equations in the classical treatment implies the existence of laser enhancement     

Laser scanning microscopy

In conventional light microscopy, images are formed either by direct imaging of the object at a desired magnification or by imaging the object onto a remote surface and converting the illuminance at that surface to an electrical signal. In laser scanning microscopy, the object or specimen surface is scanned point by point by a focused laser beam. The actual image or other pertinent characteristic of the object is then generated by an electronic system. Use of such scanned laser systems exists today in biomedical research, in the semiconductor microelectronics industry, and in varied other industrial inspection applications. In this paper, we review the basic principles of laser scanning microscopy, discuss advantages as compared to more conventional light microscopy, and illustrate the technique with examples of systems in use today.     

Alloying behaviour of Au-Ge/Pt ohmic contacts to GaAs by pulsed electron beam and furnace heating

Au-Ge/Pt contacts on n-type GaAs have been irradiated by a pulsed electron beam to yield excellent ohmic behaviour. Auger electron spectroscopy (a.e.s.) measurements of the depth profiles of the constituent elements in these irradiated contacts indicate that considerable intermixing of the metals with Ga and/or As is not necessary for good ohmic behaviour. Subsequent isochronal (2 min) furnace heating in H2 of these contacts at different temperatures shows that the Au-Ge/Pt metallisation system is highly reactive, with the inter mixing and the ohmic behaviour being a strong function of the furnace temperature. From a.e.s. measurements the important role of Ge as a dopant in generating a heavily doped GaAs layer at the metal-GaAs interface responsible for the ohmic character of the contacts is confirmed. Low specific contact resistance is closely related to the ability in incorporating Ge in a shallow GaAs layer during the alloy cycle.     

激光束的分类

对激光光学中一个十分有意义的论题,即激光束的分类作了综述和分析。基于二阶矩方法和维格纳分布函数,激光束可以按照其空间对称性分为无像散光束、简单像散光束和复杂像散光束。另一方面按空间相干性激光束可分为部分空间相干光和完全空间相干光。对各类激光束的独立特征参数及其联系作了分析。     

Laser annealing of capped and uncapped GaAs

Ion-implanted GaAs samples have been annealed using a Q-switched ruby laser. Both Si3N4 capped and uncapped samples decomposed and gallium precipitates were formed at the surface. The gallium could be removed by dissolution in HCl to leave high-quality GaAs.     

Electron beam induced current (EBIC) as a function of the angle of incidence of the electron beam in a scanning electron microscope (SEM)

The paper presents an analysis of the Electron Beam Induced Current as a function of the angle of incidence of an electron beam. A SEM experiment under steady-state conditions for a silicon diode structure has been performed. Two simple theoretical models have been considered.     

透射电镜与扫描电镜分析

文章简要介绍了透射电镜和扫描电镜两种当前主要的电子显微分析方法的应用,比较了它们的结构和工作原理,讨论了各自的应用范围以及发展方向,指出将两者有机结合可以得到比较全面的材料分析结果。     

Laser annealing of ainc implanted GaAs

GaAs samples implanted with 1.10¹⁵ zinc ions/cm³ have been annealed using pulses from a ruby laser operating in the freely generated mode. The percentage electrical activities and peak carrier concentrations were found to depend on the implant temperature, the laser energy density and the number of pulses. The maximum hole concentration measured was about 1.10²⁰ cm^?3 following irradiation with four pulses of 3 J/cm². Significant residual damage remained after single pulse irradiation at this energy density value. However, the carrier mobilities were similar to values for good single crystal GaAs.     

THE GROWTH OF MONOCRYSTALLINE SILICON THIN FILM ON INSULATOR (SOI) BY SCANNING ELECTRON BEAM

An experiment for preparation of SOI films by using the scanning electron beam to modify the polycrystalline silicon on SiO2 is presented. This method takes on the epitaxial lateral growth of liquid phase with the crystallon to form monocrystalline silicon films. The effects of the beam power density, scanning velocity, temperature of the substrates and the construction of samples on the quality of the monocrystalline silicon films were discussed. A good experimental result has been obtained, the monocrystalline silicon zone is nearly 200×25μm2.     

Comparative study of depth and lateral distributions of electron excitation between scanning ion and scanning electron microscopes

In order to study the contrast difference between scanning ion microscopes (SIM) and scanning electron microscopes (SEM), the depth and lateral distributions of secondary electrons escaped from surfaces of 17 metals with atomic numbers, Z2, of 4-79 were calculated for bombardment with 30 keV Ga ions and for 10 keV electrons. For both projectiles, the excitation depth generally decreased with increasing Z2, while showing the same periodic change as the secondary-electron yield. However, an opposite trend in Z2 dependence between the Ga ion and electron bombardments was calculated with the lateral distribution of secondary electrons escaped from the surface. Except for low Z2 metals, the lateral distribution, which is much narrower for 30 keV Ga ions than for 10 keV electrons, indicates that the spatial resolution of the secondary-electron images is better for SIM than for SEM, if zero-sized probe beams are assumed. Furthermore, the present calculation reveals important effects of electron excitation by recoiled material atoms and reflected electrons on the lateral distribution, as well as the secondary-electron yield, for the Ga ion and electron bombardments, respectively.     

Moving beam helical CT scanning

Images generated with helical scanning are degraded by partial volume artifacts caused by an increased slice thickness when compared to conventional computed tomography (CT) scanning. The slice thickness for a helical scan is proportional to the sum of the thickness of the fan of radiation and the distance the patient moves during data acquisition. The authors present a method called moving beam helical scanning (MBHS) which significantly reduces the partial volume artifacts caused by helical scanning. The key element of MBHS is a rotatable collimator that is placed between the X-ray source and the patient. As the patient is translated, the collimator is used to aim the fan on a fixed position in the patient. Once sufficient data are obtained to reconstruct a slice, the collimator is quickly reset to scan a target in the next slice. The authors examined the performance of MBHS by scanning wires and phantoms on a modified scanner. The full-width-at-tenth-maximum of the slice profile at iso-center for MBHS is identical to conventional CT versus a 59% increase for conventional helical scanning. It is concluded that MBHS can be used to obtain the scan rate advantages of helical scanning with image quality comparable to conventional scanning.     

The scanning electron microscope

The scanning electron microscope combines the techniques of the cathode-ray tube and the conventional electron microscope?both considered indispensable to modern technology. The SEM, which presents a picture having a distinct three-dimensional appearance, is finding application in the examination of wood fibers in connection with paper manufacture, of surfaces undergoing ionic bombardment, and of corrosion. At the present time, one of the most pressing problems is to reduce its total cost.