内建电场调控光生电荷分离效率的研究进展

光催化技术是解决现今环境污染和能源危机的重要手段之一,然而大部分催化剂的光催化效率较低,提高光生电荷的分离是提高光催化效率的一种有效方法.首先对催化剂的光催化原理进行了概述;结合近年来国内外在提高光生电荷分离效率方面取得的最新成果及进展,从内建电场的产生机理入手,综述了半导体p-n结、异相结、极化表面和铁电材料极化对光...     

XAFS applications in semiconductors

X-ray absorption fine structure （XAFS） has experienced a rapid development in the last three decades and has proven to be a powerful structural characterization technique nowadays. In this review, the XAFS basic principles including the theory, the data analysis, and the experiments have been introduced in detail. To show its strength as a local structure probe, the XAFS applications in semiconductors are summarized comprehensively, that is, thin films, quantum wells and dots, dilute magnetic semiconductors, and so on. In addition, certain new XAFS-related techniques, such as in-situ XAFS, micro-XAFS, and time-resolved XAFS are also shown.     

基于TEC的大功率LD恒温控制系统的研究

TEC存在功率有限、制冷效率低的问题,在用于大功率半导体激光器的温度控制时,常常无法达到所需的制冷效果.通过理论研究、软件仿真和实验验证,总结和提出了根据LD热负载选择TEC的理论依据和方法,以及与之匹配的大功率散热结构的设计优化准则.经实验验证,根据此原则设计的温控系统可在环境温度-40～55℃时,对30 W的LD实现恒温控制,温控范围20～40℃,温控精度0.5℃,实验结果表明此方法可以提高系统的整体效率,在设计大功率半导体激光器温控系统时具有一定的参考价值.     

新形势下中国半导体设备的发展对策

随着半导体生产热点全球性地向中国转移,国内的半导体设备行业面临着空前的巨大机会和前所未有的严峻挑战。在全面深入分析半导体设备特性以及行业发展特点的基础上,指出核心技术是产品性能和成本即市场生命力的决定性因素。针对当前国内半导体设备开发中普遍存在的偏差与误区,提出了努力促进企业自身对核心技术全面深入的掌握,不断增强其自主持续创新能力的半导体设备发展对策。以全自动引线键合机开发和市场的具体详细实例印证这一论断。     

Optical constants of CuO and ZnO particles in the terahertz frequency range

The optical constants (complex dielectric function) of CuO and ZnO particles in polyethylene pellets are measured by terahertz time-domain spectroscopy. The determination of the dielectric properties of these materials is of interest for energy-storage applications, for instance. Maxwell-Garnett theory is used to extract the contribution to the frequency-dependent optical constants of the oxide powders. The validity of the assumptions of Maxwell-Garnett theory are experimentally verified and self-consistency of the results of the model confirmed. On this basis, experimental complex permittivity values for isotropic CuO and ZnO oxide powders are reported in the 100 GHz-3 THz range.     

外腔激光器光子寿命对波长转换特性的影响

作为自动交换光网络中的核心器件,全光波长转换器发挥着重要作用。本文根据光纤光栅外腔半导体激光器(FBG-ECL)实现波长转换的理论模型,重点研究光子寿命对波长转换器调制特性的影响;利用速率方程,数值求解了不同光子寿命下波长转换特性;通过自行搭建的基于FBG-ECL的实验平台进行了实验分析,发现理论分析和实验数据是吻合的。     

基于声光调谐的扫频光源

提出了一种利用声光调谐方法进行滤波的扫频光源来提高它的输出稳定性。阐述了实现光源稳定输出的原理和方法,研究和分析了光源的相关参数。该系统采用声光调谐的方法代替机械滤波的方式。在一个环形腔内,使用半导体光放大器(SOA)作为增益介质,声光可调谐滤波器(AOTF)作为波长选择元件,利用声光调谐的原理对腔内的光进行选频滤波。在280mA的注入电流下,得到了1 294~1 368nm的扫频光源,其中心波长为1 328nm,半高全宽为51nm,扫频速度为3 731Hz,环形腔内直接输出的光功率为1.14mW。由于AOTF是电控制元件,波长的调谐不需要机械移动部件,故提高了系统的稳定性,输出光谱的重复性也很好。实验显示:通过这种方法获得的扫频光源输出稳定,基本满足扫频相干层析成像系统对扫频光源工艺参数的要求。     

Effect of rare-earth doping on the electrical and photoelectrical properties of furazano [ 3,4-b] piperazine (FP) thin-film devices

Schottky diodes of rare-earth, praseodymium (Pr)-doped and samarium (Sm)-doped furazano [3,4-b] piperazine (FP), sandwiched between Al and indium-tin oxide (ITO) were made by a spin-coating technique. The diodes, in which doped FP behaves as a p-type organic semiconductor, exhibit rectification behaviour. The p-type semiconductivity and rectification properties of the devices improve with rare-earth doping. The electrical effects observed in these devices are explained in terms of the p-type semiconducting behaviour of the doped FP thin films and the formation of a blocking contact (Schottky barrier) with the Al electrode and ohmic contact with the ITO electrode. Various electrical parameters such as carrier mobility, position of Fermi level, free carrier concentration, trap density, trap level and conductivity of doped FP are calculated and discussed. It is found that the position of the Fermi level shifts toward the valence band on rare-earth doping; concentration of free carriers and carrier mobility increase on doping. From the capacitance-voltage (C-V measurements, various electrical parameters such as barrier height, density of ionized acceptor atoms and depletion layer width are calculated and discussed. From the action spectra and absorption spectra it is confirmed that the Al-doped FP interface forms a Schottky barrier and the ITO-doped FP interface shows ohmic contact. The photovoltaic measurement on the two devices reveals that the short circuit current, open circuit voltage, fill factor and power conversion efficiency increase on rare-earth doping.     

半导体激光二极管触发GaAs光导开关

半导体激光二极管触发下砷化镓（GaAs）光导开关工作于雪崩模式,为此设计了异面体结构的GaAs 光导开关以提高开关场强.设计的开关芯片厚度为2 mm,电极间隙为3 mm,利用半导体激光二极管对开关进行触发实验.当开关充电电压超过8 kV 后,开关输出脉冲幅度显著增强,输出脉冲前沿快于光脉冲,开关开始雪崩工作模式.随着开关电场不断增加,开关输出电压幅值也线性增加,但开关输出波形没有改变.对开关抖动进行测试,其测试结果显示开关偏压对抖动影响很大,随着开关偏压增加,开关抖动减小,当开关偏压升至15 kV 时,开关获得最小抖动约500 ps.     

利用半导体激光器功率—电流曲线斜率的变化控制AR膜的镀制

研究了不同偏置条件下半导体激光器的微分输出功率与端面反射率的关系,为主动法控制半导体光放大器端面减反射膜的镀制提供了必要的使用判据。镀膜实验证实了理论预测,使用本判据有助于提高镀膜的可靠性。