SiC materials-progress, status, and potential roadblocks

SiC materials are currently metamorphosing from research and development into a market driven manufacturing product. SiC substrates are currently used as the base for a large fraction of the world production of green, blue, and ultraviolet light-emitting diodes (LEDs). Emerging markets for SiC homoepitaxy include high-power switching devices and microwave devices for S and X band. Applications for heteroepitaxial GaN-based structures on SiC substrates include LEDs and microwave devices. In this paper we review the properties of SiC, assess the current status of substrate and epitaxial growth, and outline our expectations for SiC in the future.     

Gallium nitride emitting devices preparation and properties

GaN:Zn//Al₂O₃ electroluminescent devices have been obtained with a wide range of emitted colours (blue, green, yellow and red) ; theses devices have high potential since external quantum efficiencies greater than 1 % and power efficiencies of about 10⁻³ have been reported. On the other hand, from the literature it seems that each colour is obtained randomly, since apparently the same method of preparation is used. We show that the properties of GaN:Zn (conductivity type, cathodoluminescence (peaks and efficiency)) can not be related uniquely to the partial pressure of zinc during the growth, but it is also necessary to take into account the partial pressure of HCl and the thickness of the π layer in order to obtain a satisfactory representation of these properties. From this knowledge, one can deduce the different parameters for growing layers for devices and control their properties. The device fabrication consists of the deposition of a Zn doped thin layer, which is nearly insulating but with p tendency (π layer), onto a Zn doped n type layer. It is demonstrated that the characteristics of the devices (I(V) curves, electroluminescent peaks and efficiencies are related to the characteristics of the π layer and on the transition from n to π. Blue LEDS with characteristics very similar to p-n junction characteristics have been obtained. This work has been supported by DGRST (Délégation a la Recherche Scientifique et Technique).     

Gallium nitride based high power heterojunction field effecttransistors: process development and present status at UCSB

The development of GaN based devices for microwave power electronics at the University of California, Santa Barbara (UCSB), is reviewed. From 1995 to 2000, the power performance of AlGaN/GaN-on-sapphire heterojunction field effect transistors improved from 1.1 W/mm to 6.6 W/mm, respectively. Compensating the disadvantages of the low thermal conductivity of the sapphire substrate through heat management via flip chip bonding onto AlN substrates, large periphery devices with an output power of 7.6 W were demonstrated. UCSB also fabricated the first GaN based amplifier integrated circuits. Critical issues involved in the growth of high quality AlGaN/GaN heterostructures by metal-organic chemical vapor deposition and the device fabrication are discussed     

NCKU and Aixtron co-operate on dilute nitride materials

Aixtron and Taiwan’s National Cheng Kung University of Tainan (NCKU) have started the next phase of their joint technology co-operation to develop GaInAsN based optical and electronic devices.This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.     

Future challenges and directions for nitride materials and lightemitters

A review is presented of future issues on wide-bandgap group-III nitride materials and device technology for optoelectronic and high-temperature devices such as LEDs     

氮(氧)化物荧光粉的合成与发光性能

为了制备高性能的白光LED,发光性能好的荧光粉是必不可少的。氮(氧)化物荧光粉有着发光效率高、可进行光谱剪裁、绿色环保、热稳定性好的优点,可以成为制备白光LED的主要的荧光粉材料。本文综述了近几年来在氮(氧)化物荧光粉的晶体结构特征、制备方法,发光性质及其在高亮度、高显色白光LED封装应用的最新进展,并指出该领域研究过程中存在的问题:(1)含有不同非金属成份的氮(氧)化物新基质很少,(2)关于计算荧光粉晶体场变化的理论研究很少,(3)目前单一基质白光发射荧光粉的发射普遍存在红色发射成分缺乏或不足、显色指数不高等问题。对该领域的发展趋势做出了展望,希望推动新型高效白光LED用发光材料的研究,继而提高白光LED研究应用水平。     

Growth and characterisation of dilute antimonide nitride materials for long-wavelength applications

The addition of small amounts of nitrogen to III-V semiconductors leads to a large degree of band gap bowing, giving rise to band-gaps smaller than in the associated binary materials. The incorporation of active nitrogen has been previously demonstrated for InN_xSb_1−x (x?0.7%) and GaN_xSb_1−x (x?1.75%) material; however, the as-grown carrier concentrations precluded incorporation into a device structure. Here we report the reduction in the as-grown carrier concentration in InNSb by annealing, whilst retaining the active nitrogen content. FTIR absorption measurements show the first direct experimental evidence of narrowing of the InSb bandgap due to nitrogen incorporation. As an alternative route to defect reduction and device compatible material we report on the growth of Ga_1−yIn_yN_xSb_1−x with 0?y?30% and x=1.6±0.2% and demonstrate near lattice matching of the material to GaSb.     

E罗兰系统研究现状和进展

文章介绍了无线电导航系统,归纳总结了卫星导航系统存在的风险因素以及陆基无线电导航系统的优势,指出了罗兰导航系统是星基导航系统最理想的备份系统;然后对罗兰系统做了概述,对罗兰系统的发展历史和应用现状做了阐述;最后,说明了E罗兰建设的必要,给出了国外(英国和韩国)E罗兰系统建设情况。     

Research progress of Si-based germanium materials and devices

Si-based germanium is considered to be a promising platform for the integration of electronic and photonic devices due to its high carrier mobility, good optical properties, and compatibility with Si CMOS technology. However, some great challenges have to be confronted, such as: (1) the nature of indirect band gap of Ge; (2) the epitaxy of dislocation-free Ge layers on Si substrate; and (3) the immature technology for Ge devices. The aim of this paper is to give a review of the recent progress made in the field of epitaxy and optical properties of Ge heterostructures on Si substrate, as well as some key technologies on Ge devices. High crystal quality Ge epilayers, as well as Ge/SiGe multiple quantum wells with high Ge content, were successfully grown on Si substrate with a low-temperature Ge buffer layer. A local Ge condensation technique was proposed to prepare germanium-on-insulator (GOI) materials with high tensile strain for enhanced Ge direct band photoluminescence. The advances in formation of Ge n⁺p shallow junctions and the modulation of Schottky barrier height of metal/Ge contacts were a significant progress in Ge technology. Finally, the progress of Si-based Ge light emitters, photodetectors, and MOSFETs was briefly introduced. These results show that Si-based Ge heterostructure materials are promising for use in the next-generation of integrated circuits and optoelectronic circuits.     

The status of silicon carbide and related materials

The 6th International Conference on Silicon Carbide and Related Materials (ICSCRM) was held in Kyoto, Japan, from September 18–21 1995. Emerging commercial applications were a major theme of the meeting writes Simon Lande of Magus Research     

磁电复合材料的研究现状及展望

介绍了国内外磁电复合材料的研究历史和制备方法,如混相法,铁电/铁磁材料层状复合法。探讨了磁电复合材料应用研究中亟待解决的问题,指出了今后的发展趋势是改进复合材料的设计方法、制备工艺和集成器件应用。     

超分辨成像方法研究现状与进展

光电成像系统受到衍射极限和像元分辨率的制约,但研究者们从未停止过脚步来突破这一限制。本文介绍了近年来开展的各种超分辨成像方法和技术,包括应用于荧光显微成像的受激发射损耗技术、结构光照明技术、光激活定位技术与随机光学重构超分辨成像技术;可应用于显微系统、光存储与眼底成像的光瞳滤波技术与径向偏振光超分辨聚焦技术;应用于空间探测的合成孔径技术、光子筛成像技术、超振荡透镜技术、亚像元技术与焦平面编码技术。主要讨论了以上超分辨方法的原理、实现手段与目前发展水平。     

高速光学模数转换器的研究现状及进展

高速高精度模数转换器（Analog-to-digital Converters,ADC）是现代数字信息处理系统中的关键组成部分,现有的电子模数转换器存在运行速率严重受限的难题,因此引入光学方法实现高速高精度模数转换成为研究的热点。本文重点针对高速光学模数转换器的研究现状及进展进行了探讨,并对光学辅助、光采样电量化、电采样光量化以及全光采样量化目前4种最主要的光学模数转换器的原理、结构和最新的研究进展进行了详细的介绍。     

氧化物忆阻器材料及其阻变机理研究进展

忆阻器是目前材料和电子领域的研究前沿和热点,氧化物材料在忆阻器研究中具有重大价值。本文综述了近年来研究较多的几种典型氧化物忆阻器材料,包括TiO_2、SiO_x、HfO_x、Al_2O_3、ZnO、ZrO_2、TaOx以及ZnSnO_3等,并介绍了导电细丝机制、氧化还原机制、边界迁移机制以及相变机制等四种常见的阻变机理,展望了未来忆阻器材料研究的方向与重点。     

无铅喷金材料的发展现状与展望

介绍了国内外无铅喷金材料的发展过程和最新研究动向,综述了无铅喷金材料的分类和性能以及最新生产技术。对国内外专利申请和授权情况进行了总结,指出今后的发展方向主要是提高无铅喷金材料的性价比和适应性,同时开发高效节能的生产技术。     

驻极体声传感器及其储电材料的现状

综述了驻极体声传感器及其储电材料近年来的迅猛发展。传统的FEP(tetrafluoroethylene—hexa—fluoropropylene copolymer)极体电容式声传感器及以铁电聚合物PVDF(poly vinylidene fluoride)家族为芯片的声传感器和超声抉能器仍焕发着青春活力。Si基微型驻极体声传感器的理论和实验研究已经日趋成熟，而用空间电荷型多孔聚合物驻极体压电薄膜为芯片可望研制出新一代声电和电声传感器、压力传感器和驱动器。     

太赫兹波段液晶材料的应用及研究进展

液晶材料在太赫兹频谱的应用正在兴起。首先介绍了基于液晶材料设计的太赫兹功能器件的最新研究进展,然后分别从实验和理论角度总结了太赫兹光谱学的基本原理,最后展望了本领域未来的研究方向——研究液晶分子结构对其太赫兹光电特性的影响规律。     

Recent progress and future prospects of high-entropy materials for battery applications

<正>Due to the energy crisis caused by limited fossil fuel reserves,extensive use of the renewable energy sources such as wind or solar energy is deemed to replace the use of traditional fossil fuels in the future^[1-3].However,most renewable energy sources face the same problem,which is the intermittency of energy.For example,solar energy cannot be utilized at night.That means the continuous energy demand required for large-scale power grids can’t be satisfied by a single solar p...