镓三相点容器的金属充灌方法

本文介绍了中国计量科学研究院镓三相点容器研制中高纯镓的充灌的方法———负压法。其利用容器内外的压差 ,将高纯镓充入到容器内 ,同时 ,又可避免高纯镓被氧化。     

一种新的更为简单的制作镓熔点容器的方法

本文介绍了一种新的更为简单、方便的制作镓熔点容器的方法.该方法利用压力平衡的原理,精确控制所充入气体的压强.并将新方法制作的镓熔点容器与国家基准的镓熔点容器进行比对.     

一种新的更为简单的制作镓熔点容器的方法

本文介绍了一种新的更为简单、方便的制作镓熔点容器的方法。该方法利用压力平衡的原理，精确控制所充入气体的压强。并将新方法制作的镓熔点容器与国家基准的镓熔点容器进行比对。     

镓熔点温坪复现研究

镓熔点是ITS-90国际温标中重要的定义固定点,在温度计量研究中起着重要作用。由于高纯镓从液态转化为固态时,体积膨胀约3.1%,传统玻璃外壳的镓熔点容器在冻制过程中很容易造成损坏。为了解决这一难题,设计了一种具有金属外壳的镓熔点装置,以该装置为对象,开展了2种不同镓熔点复现方法和2种不同复现装置对镓相变温坪影响方面的研究,并与国外同类型装置的性能进行了比较。实验结果表明:不同镓点容器复现的镓熔点温度在0.02 mK范围内一致,高纯镓中的微量杂质是造成差异的主要原因;外液-固界面复现方法比双液-固界面复现方法得到的温坪值低0.09 mK;不同复现装置对镓熔点温坪的影响较小。     

MCP和Recapture公司联合收购炼镓厂

MCP集团和Recapture金属公司联合收购了德国的Ingal Stade原镓生产厂，但GEO镓业公司的镓提纯、市场及销售部门不包括在内。MCP在英国、德国、中国和美国均设有工厂，生产铋、铟、硒、碲和镓等的金属、合金及化工产品。MCP将99．99％的镓精制成高纯镓（6个“9”或7个“9”）用于三氧化镓生产，而后者则是有机金属化合物的原料。     

世界高纯镓发展趋势

高纯镓主要是制备砷化镓、磷化镓的原料。砷化镓是化合物半导体的核心材料。磷化镓是继砷化镓材料之后的又一竞争领域。可以说,砷化镓和磷化镓如同“两个轮子”推动着化合物半导体材料的发展。日本是世界上砷化镓、磷化镓材料的主要生产国家。据预测,日本1988年砷化镓材料市场规模达到83亿日元(需要量达到12200kg);磷化镓95亿日元(需要量达到9800kg)。由于世界上砷化镓、磷化镓需要量不断增加,因而作为其原料之一的高纯镓也大量消耗。本文就镓、高纯镓的发展状况简单介绍如下。     

一种新型结构的镓三相点容器

本文介绍了计量院研制的新型结构的镓三相点容器及镓三相点的复现方法。并将两个镓三相点容器与镓熔点容器进行了比对 ,结果表明 :两个镓三相点容器所复现的镓三相点温度与镓熔点温度的差值分别为1 85mK、1 71mK ;通过分析认为镓三相点容器间的温差 (0 1 4mK)主要是镓样品所含杂质成分的差异引起的。     

镓熔点容器

介绍了中国计量科学研究院于１９９１年研制成功并通过鉴定的镓熔点全密封容器主要技术指标（长期稳定性容器间的差）。至目前仍保持相当好，两年来向国内、外用户提供了数个这种客器，在使用中技术性能也很满意．     

新型镓熔点自动复现装置

介绍了中国计量科学研究院新型镓熔点自动复现装置, 该装置的固定点炉采用半导体三段冻制及加热技术实现了镓熔点复现的自动化, 通过精密控温及合理的结构设计获得优良的温度稳定性与均匀性。该装置镓熔点使用当前最新提纯技术的99.999 99%高纯镓金属及完善的灌注技术。实验结果显示, 该固定点装置温坪持续了70 h以上,前20%～80%温坪变化小于0.15 mK,复现性为0.07 mK, 该装置的扩展不确定度为0.36 mK（k=2）。     

镓三相点容器的研制

近年来,镓三相点作为新的温度固定点的研究已经得到了广泛的重视。本介绍了镓三相点容器的制作工艺、冻制过程及复现技术。实验结果表明,镓三相点的温度值为29.7666℃     

Gallium telluride heterojunctions

The photoelectric properties of In₂O₃-GaTe and GaTe-InSe heterojunctions were investigated. Their characteristics were described using a diffusion model of the heterojunction. Some deviation of the characteristics from ideal was observed for In₂O₃-GaTe heterojunctions as a result of the presence of a thin dielectric layer at the heteroboundary. Qualitative energy band diagrams were constructed for the heterojunction and their photosensitivity was determined in the range 0.33–1.0 μm. Pis’ma Zh. Tekh. Fiz. 25, 29–33 (January 26, 1999)     

New SMU Gallium Fixed-Point Cells

In the framework of the European research project EURAMET 732, the Slovak Institute of Metrology (SMU) built three primary gallium fixed-point cells of different designs. The cells are designed for the calibration of the long-stem SPRT. In regard to the procedure commonly used at SMU when realizing the gallium point, the cells are designed for use in a stirred liquid bath. This article provides information about the cell designs, materials used, method of filling, and results of the performed experiments. The experiments were focused on the study of the cells?? metrological characteristics, some effects that could influence the melting-point temperature and the effect of the melted metal fraction on the immersion profile. New cells were compared with the SMU reference gallium cell.     

Gallium arsenide digital integrated circuits

The motivations behind the development of GaAs integrated circuits (IC) are two-fold: to integrate high speed logic with optical sources and to meet the increasing demand of realising LSI/VLSI with higher speed and lower power dissipation for large scale computer applications. GaAs gigabit circuits have been growing in complexity to more than 3000 gates on a single chip. Although this is encouraging, more efforts are needed to improve production yield. By far the most work on GaAs digital IC has been done using MESFET as the active devices. MOSFET technology is yet to mature from the practical IC point of view. The logic gate types used in circuits are predominantly of the enhancement-mode driver and depletion-mode load configuration (E/D). A brief survey of the state-of-the-art of GaAs digital IC is presented. Implemented circuits are described and compared with those achieved through various technologies. GaAs gate arrays, multipliers, accumulators and memories are discussed. At liquid N₂-temperature, a switching time of 5·8 ps/gate has been achieved for 0·35μm gate devices. This and similar other results lead to the conclusion that at the VLSI level of future Gbit circuits, GaAs devices in the form of HEMT operated at 77 K can outperform Si-devices. At′ LSI complexities, experimental GaAs MESFET and 300 K HEMT have a lead on Sicircuits—it is then this range in which Gbit/GaAs should find their application.     

Gallium nitride-based potentiometric anion sensor

The gallium nitride (GaN) semiconductor is used as the sensing element for the development of a potentiometric anion sensor. The anion recognition mechanism is based on the selective interaction of anions in solution with the epitaxial Ga-face polarity GaN (0001) wurtzite crystal film grown on sapphire. The native GaN crystal is used for the development of an ion blocked sensor. The potential is based on the Volta potential, generated at the semiconductor/solution interface and within the Helmholtz layer, due to specifically adsorbed anions. The selectivity of the sensor is based on the direct interaction of the anionic ligand with the outer electron-defective gallium atoms; thus, it is not dependent on the lipophilicity of the adsorbed charged species. The chemical resistivity of the GaN crystal provides sensors with excellent lifetime, signal stability, and reproducibility.     

Gallium nitride based logpile photonic crystals

We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ～100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.     

Non-destructive Evaluations of Gallium Nitride Nanowires

We have calculated the second and third order elastic constants of GaN nanowires at room temperature validating the interaction potential model. The ultrasonic attenuation and velocity in the nanowires are determined using the non-linear elastic constants for different diameters (97 nm -160 nm) of the wires at the nanoscale. Where possible, the results are compared with the experiments. Finally we established the correlation between the size dependent thermal conductivity and the ultrasonic attenuation of the nanowires.     

Gallium nitride nanowires doped with magnesium

GaN nanowires doped with Mg have been synthesized on Si (111) substrate through ammoniating Ga₂O₃ films doped with Mg under flowing ammonia atmosphere. The Mg-doped GaN nanowires were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The results demonstrate that the nanowires were single crystalline with hexagonal wurzite structure. The diameters of the nanowires ranged 20-30 nm and the lengths were about hundreds of micrometers. The intense PL peak at 359 nm showed a blueshift from the bulk band gap emission, attributed to Burstein-Moss effect. The growth mechanism of the crystalline GaN nanowires is discussed briefly.