Desorption and Ripening of Low Density InAs Quantum Dots

In this paper, combining low deposition rate with proper growth temperature, we have developed a way to prepare very low-density quantum dots (QDs) suited for the study of single OD properties without resorting to submicron lithography. Experiment results demonstrate that InAs desorption is significant during growing the low density QDs. Ripening of InAs QDs is clearly observed during the post-growth annealing. Photoluminescence spectroscopy reveals that the emission wavelength of low density InAs QDs arrives at 1332.4 nm with a GaAs capping layer.

Tuning of emission wavelength of InAs/GaAs quantum dots sandwiched by combination layers

We investigate about controlling of photoluminescence (PL) wavelengths of InAs/GaAs self-assembled quantum dots (QDs) sandwiched with combination strained-buffer layer (CSBL) and combination strained-reducing layer (CSRL). The emission peak position of QDs is red-shifted to 1.37 mu m. The density of the QDs is increased to 1.17x10(10) cm(-2). It is indicated that optical properties of QDs could be improved by optimizing of the buffer and covering layers for the QDs. These results may provide a new way to further developing GaAs-based 1.3 mu m light sources.

Influence of fluorine on radiation-induced charge trapping in the SIMOX buried oxides

Charge trapping in the fluorinated SIMOX buried oxides before and after ionizing radiation has been investigated by means of C-V characteristics. Radiation-induced positive charge trapping which results in negative shift of C-V curves can be restrained by implanting fluorine ions into the SIMOX buried oxides. Pre-radiation charge trapping is suppressed in the fluorinated buried oxides. The fluorine dose and post-implantation anneal time play a very important role in the control of charge trapping.

practical type checking of functions defined on context-free languages

A type checking method for the functional language LFC is presented. A distinct feature of LFC is that it uses Context-Free (CF) languages as data types to represent compound data structures. This makes LFC a dynamically typed language. To improve efficiency, a practical type checking method is presented, which consists of both static and dynamic type checking. Although the inclusion relation of CF.languages is not decidable,a special subset of the relation is decidable, i.e., the sentential form relation, which can be statically checked.Moreover, most of the expressions in actual LFC programs appear to satisfy this relation according to the statistic data of experiments. So, despite that the static type checking is not complete, it undertakes most of the type checking task. Consequently the run-time efficiency is effectively improved. Another feature of the type checking is that it converts the expressions with implicit structures to structured representation. Structure reconstruction technique is presented.

螺旋板式蒸发器在地热电站中的应用

利用地下热水来加热低沸点工质(如氯乙烷、正丁烷、异丁烷、氟利昂等)，使它变为蒸汽，然后去驱动汽轮发电机组发电的“双流系统”地热发电，是一种有发展前途的地热发电方式。这种发电方式的一个重要问题是如何选择一种高效，小体积的换热设备。我们在广东省丰顺县邓屋双流系统地热电站建设中，选用了螺旋板式换热器作为异丁烷蒸发器和预热器。其中预热器是选用了苏州化工机械厂的系列产品不可拆螺旋板换热器，型号为I16 T70—1.0/1200—10。蒸发器为我们自行设计，结

BREAKING UP OF MISFIT DISLOCATIONS IN GAASIN0.3GA0.7AS/GAAS HETEROSTRUCTURE

The effect of GaAs cap layer with different thicknesses in the GaAs/In0.3Ga0.7As/GaAs heterostructure on misfit dislocation is investigated with transmission electron microscopy, and it is found that lines of misfit dislocation break up and move out of the structure when the GaAs cap layer thickness exceeds a certain amount. The breaking up and moving out of misfit dislocations, initially confined in the (001) substrate/InGaAs epilayer interface, occur mainly along the [110] direction on the interface in the structure. (C) 1995 American Institute of Physics.

GaAs/GaInNAs多量子阱谐振腔增强型长波长光探测器

报道了一种具有高速响应特性的GaAs基长波长谐振强增强型(RCE)光探测器,它采用分子束外延技术(MBE)在GaAs衬底上直接生长GaAs/AlAs布拉格反射镜(DBR)和GaInNAs/GaAs多量子阱吸收层而形成,解决了GaAs系材料只能对短波长光响应的问题,实现了GaAs基探测器对长波长光的响应.该器件在峰值响应波长1 296.5 nm处获得了17.4%的量子效率,响应谱线半宽为11 nm,零偏置时的暗电流密度8.74×10-15 A/μm~2,具有良好的暗电流特性.通过RC常数测量计算得到器件的3 dB带宽为4.82 GHz.

沈阳市城市景观生态学研究

全球正在迅速工业化、城市化和现代化，当今世界一切环境污染、生态破坏问题无一不与工业化、城市化过程相联系。城市的发展对生态学提出了挑战。同样，景观生态学如何服务于城市，如何为城市的可持续发展，解决城市所面临的各种环境问题，这是广大景观生态学工作者义不容辞的责任。本文应用GIS技术，以沈阳市城市核心区（三环高速公路以内区域）为研究对象，应用景观生态学的理论与方法，探讨城市景观结构及景观与生态环境质量的关系，运用尺度分析方法来进行景观分区，探讨城市景观生态规划问题，以增加城市景观生态研究实例，补充与完善景观生态的理论与方法，为沈阳市城市景观生态建设提供理论依据。通过对其空间结构分析得出，该研究区内的景观多样性指数为2.847，优势度指数为1.059，聚积度指数为0.803。研究表明，在城市景观中存在着一明显的交错带，在该带中，景观多样性最大，。斑块数破碎化指数最大，优势度最小，均匀度最大，表明该带异质性最大，它处在郊区农业生态系统向城市中心过渡的过渡带，由于两个系统各自的能流与物流特征都可在该带内出现，所以集中了城市系统内部信息和郊区农业生态系统信息，使得该带内信息量最大，生态过程最强，这一交错带是信息流集中和汇集的焦点，是景观生态的活跃地带，对沈阳市而言，该带是一环路与二环路之间的区域。城市中人为利用开发程度从市中心向周边地区扩张，沈阳市建成区用地扩张的主要特点是条带发展带动区域扩张，局部突出促进整体发展，局部带动区域，区域带动全市，使城市用地规模不断增加，城区界限不断外延。尺度分析在景观生态学中越来越受到重视，本文应用尺度分析方法把沈阳市城市景观分为12个景观区，通过分区研究表明，沈阳市景观区布局不合理。结构决定功能，沈阳市城市环境质量状况与其景观结构有着密切的关系。不同类型的景观中，污染物含量的高低，因污染物的不同而异。TSP、SO2、NOx是工业景观中最多，绿地景观中最少，CO是道路中最多，绿地中最少。工业景观是环境污染的主要来源之一，这与工业本身的特点密切相关。沈阳市大气环境质量的空间分布状况与其景观结构密不可分。最后对城市景观生态规划的理论问题作了探讨，并提出了沈阳市城市景观生态规划的基本思路。