A new type of photoelectric response in a double barrier structure with a wide quantum well

We have calculated the photoelectric response in a specially designed double barrier structure. It has been verilied that a transfer of the internal photovoltaic effect in the quantum well to the tunnelling transport through above-barrier quasibound states of the emitter barrier may give rise to a remarkable photocurrent.

Effect of rapid thermal annealing on GaInNAs/GaAs quantum wells grown by plasma-assisted molecular-beam epitaxy

We have studied the effect of rapid thermal annealing (RTA) on GaInNAs/GaAs quantum wells (QWs) grown by molecular-beam epitaxy using a dc plasma as the N source. It was found that RTA at low temperature (LT, 650 degrees C) and high temperature (HT, 900 degrees C) could both improve the QW quality significantly. To clarify the mechanism of quality improvement by RTA, a magnetic field perpendicular to the path of the N plasma flux was applied during the growth of the GaInNAs layers for the sake of comparison. It was found that LT-RTA mainly removed dislocations at interfaces related to the ion bombardment, whereas, HT-RTA further removed dislocations originating from the growth. LT-RTA caused only a slight blueshift of photoluminescence peak wavelength, probably due to defect-assisted interdiffusion of In-Ga at the QW interfaces. The blueshift caused by HT-RTA, on the other hand, was much larger. It is suggested that this is due to the fast defect-assisted diffusion of N-As at the QW interfaces. As defects are removed by annealing, the diffusion of In-Ga at interfaces would be predominant. (C) 2000 American Institute of Physics. [S0003- 6951(00)01535-7].

一类密钥流生成器的相关分析

多输出逻辑函数是构造密码系统的重要工具,相关免疫性是设计安全逻辑函数的重要准则.该文利用一种较为简单的方法证明了多输出逻辑函数相关免疫性两种刻划的等价性.还对一类利用多输出逻辑函数相关免疫函数构造的密钥流生成器进行了相关性分析,证明了这种构造方法是不成立的,并不能达到构造者期望的相关免疫性,并且分别利用Walsh变换技术和线性序列电路逼近方法找出了这类密钥流生成器的漏洞,从而说明这类生成器在相关攻击下是脆弱的.

一种新型2*2 SOI热光开关

设计并制作了一种新型的SOI 2×2马赫-曾德(MZ)热光开关.这种光开关采用了深刻蚀结构的配对多模干涉耦合器,同时,为了保证单模传输和调制,在连接波导和调制臂区域采用了浅刻蚀结构.深刻蚀结构增强了多模干涉耦合器对光场的限制,有利于自映像质量的提高,从而减少了自映像损耗和不均衡度,同时也提高了制作容差.基于强限制配对干涉耦合器的新型热光开关,其插入损耗为-11.0 dB,其中包括光纤-波导耦合损耗-4.3 dB,上升和下降开关时间分别为3.5μs和8.8μs.

在硅片上沉积厚二氧化硅的火焰水解法研究

用火焰水解和高温烧结的方法在单晶硅基片上制备了厚SiO2和B2O3-P2O5-SiO2光波导包层材料.并用扫描电镜(SEM)和X射线粉末衍射(XRD)方法对其微观形貌和物相结构进行了观察和检测.重点对硅基片上沉积厚SiO2时的龟裂和析晶问题进行了深入研究.从扫描电镜照片可以看出,火焰水解法形成的SiO2粉末呈多孔的蜂窝状结构.这种粉末具有很高的比表面积,因而很容易烧结成玻璃.X射线衍射图谱表明,这种粉末是完全非晶态的.经过烧结以后,从扫描电镜照片可以明显看出硅基片上的SiO2薄膜出现龟裂.同时,X射线衍射测试结果表明有少量SiO2析晶.而通过在SiO2中掺入B2O3、P2O5,上述龟裂和析晶完全消失.用这种工艺制备的SiO2波导包层材料厚度达到20 μm以上,表面光滑、没有龟裂,而且是完全玻璃态的,可以用于制备性能优良的各种硅基二氧化硅波导器件.

GaAs、AlAs、DBR反应离子刻蚀速率的研究

采用BCl_3和Ar作为刻蚀气体对GaAs、AlAs、DBR反应离子刻蚀的速率进行了研究，通过控制反应的压强、功率、气体流量和气体组分达到对刻蚀速率的控制。实验结果表明

基于遗传算法进行加速器自动调束

　介绍了遗传算法的基本理论,及其应用于加速器调束过程中的设计要点,给出基于遗传算法进行加速器自动调束的设计方法,并编写遗传算法程序针对HIRFL中的一段束流输运线进行了计算机仿真实验,证明了基于遗传算法进行自动调束的可行性,指出了自动调束技术的未来研究方向。

Pollen record from red clay sequence in the central Loess Plateau between 8.10 and 2.60 Ma

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