Design and Fabrication of AlGaN-Based Resonant-Cavity-Enhanced p-i-n UV PDs

AlGaN-based resonant-cavity-enhanced (RCE) p-i-n photodetectors (PDs) for operating at the wavelength of 330 nm were designed and fabricated. A 20.5-pair AlN/Al0.3Ga0.7N distributed Bragg reflector (DBR) was used as the back mirror and a 3-pair AlN/Al0.3Ga0.7N DBR as the front one. In the cavity is a p-GaN/i-GaN/n-Al0.3Ga0.7N structure. The optical absorption of the RCE PD structure is at most 59.8% deduced from reflectance measurement. Selectively enhanced by the cavity effect, a response peak of 0.128 A/W at 330 nm with a half-peak breadth of 5.5 nm was obtained under zero bias. The peak wavelength shifted 15 nm with the incident angle of light increasing from 0 degrees to 60 degrees.

Anomalous temperature dependence of photoluminescence from stoichiometric GD(2)O(3-x) film

A stoichiometric Gd2O3-x thin film has been grown on a silicon (10 0) substrate with a low-energy dual ion-beam epitaxial technique. Gd2O3-x shares Gd2O3 structures although there are many oxygen deficiencies in the film. The photoluminescence (PL) measurements have been performed in a temperature range 5-300 K. The detailed characters of the peak position, the full-width at half-maximum (FWHM) and the peak intensity at different temperature were reported. An anomalous intensity behavior of the PL spectra has been observed, which is similar to that of some other materials such as porous silicon and silicon nanocrystals in silicon dioxide. Therefore, we suggest that the nanoclusters with the oxygen deficiencies contribute to the PL emission and employ the model of singlet-triplet exchange splitting of exciton to discuss the four peaks observed in the experiment. (C) 2003 Elsevier B.V. All rights reserved.

Novel folding large-scale optical switch matrix with total internal reflection mirrors on silicon-on-insulator by anisotropy chemical etching

A compact optical switch matrix was designed, in which light circuits were folded by total internal reflective (TIR) mirrors. Two key elements, 2 x 2 switch and TIR mirror, have been fabricated on silicon-on-insulator wafer by anisotropy chemical etching. The 2 x 2 switch showed very low power consumption of 140 mW and a very high speed of 8 +/- 1 mus. An improved design for the TIR mirror was developed, and the fabricated mirror with smooth and vertical reflective facet showed low excess loss of 0.7 +/- 0.3 dB at 1.55 mum.

Pseudospin in Si delta-doped InAlAs/InGaAs/InAlAs single quantum well

Magneto-transport measurements have been carried out on double/single-barrier-doped In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum well samples from 1.5 to 60 K in an applied magnetic field up to 13 T. Beating Shubnikov-de Haas oscillation is observed for the symmetrically double-barrier-doped sample and demonstrated due to a symmetric state and an antisymmetric state confined in two coupled self-consistent potential wells in the single quantum well. The energy separation between the symmetric and the antisymmetric states for the double-barrier-doped sample is extracted from experimental data, which is consistent with calculation. For the single-barrier-doped sample, only beating related to magneto-intersubband scattering shows up. The pesudospin property of the symmetrically double-barrier-doped single quantum well shows that it is a good candidate for fabricating quantum transistors. (c) 2007 Elsevier Ltd. All rights reserved.

Net-like ferromagnetic MnSb film deposited on porous silicon substrates

MnSb films were deposited on porous silicon substrates by physical vapor deposition (PVD) technique. Modulation effects due to the substrate on microstructure and magnetic properties of the MnSb film's were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and measurements of hysteresis loops. SEM images of the MnSb films indicate that net-like structures were obtained because of the special morphology of the substrates. The net-like MnSb films exhibit some novel magnetic properties different from the unpatterned referenced samples. For example, in the case of net-like morphology, the coercive field is as low as 60 Oe. (c) 2006 Elsevier B.V. All rights reserved.

Design and characteristics of quantum cascade laser-based CO detection system

National High Technology Research and Development Program of China 2007AA03Z112；Program of Ministry of Education of China 20060183030；Program of Jilin Provincial Science and Technology Department of China 20070709；Program of Bureau of Science and Technology of Changchun City 2007107

Effects of subretinal implant materials on the viability, apoptosis and barrier function of cultured RPE cells

Background: Subretinal microphotodiode array (MPDA) is a type of visual prosthesis used for the implantation in the subretinal space of patients with progressive photoreceptor cell loss. The present study aimed to evaluate the effect of materials for MPDA on the viability, apoptosis and barrier function of cultured pig retinal pigment epithelium (RPE) cells.Methods: Primary culture of pig RPE cells was performed and 24 pig eyes were used to start RPE culture. The third passage of the cultures was plated on different materials for MPDA and MPDAs. The tetrazolium dye-reduction assay (MTT) was used to determine RPE cell viability. Flow cytometry was measured to indicate the apoptosis rates of RPE cells on different materials. RPE cells were also cultured on microporous filters, and the transepithelial resistance and permeability of the experimental molecule were measured to determine the barrier function.Results: The data from all the methods indicated no significant difference between the materials groups and the control group, and the materials tested showed good biocompatibility.Conclusions: The materials for MPDA used in the present study had no direct toxicity to the RPE cells and did not release harmful soluble factors that affected the barrier function of RPE in vitro.

Electronic structure and g factors of narrow-gap zinc-blende nanowires and nanorods

The Hamiltonian in the framework of eight-band effective-mass approximation of the zinc-blende nanowires and nanorods in the presence of external homogeneous magnetic field is given in the cylindrical coordinate. The electronic structure, optical properties, magnetic energy levels, and g factors of the nanowires and nanorods are calculated. It is found that the electron states consist of many hole-state components, due to the coupling of the conduction band and valence band. For the normal bands which are monotone functions of |k(z)|, long nanorods can be modeled by the nanowires, the energy levels of the nanorods approximately equal the values of the energy band E(k(z)) of the nanowires with the same radius at a special k(z), where k(z) is the wave vector in the wire direction. Due to the coupling of the states, some of the hole energy bands of the nanowires have their highest points at k(z)=0. Especially, the highest hole state of the InSb nanowires is not at the k(z)=0 point. It is an indirect band gap. For these abnormal bands, nanorods can not be modeled by the nanowires. The energy levels of the nanorods show an interesting plait-like pattern. The linear polarization factor is zero, when the aspect ratio L/2R is smaller than 1, and increases as the length increases. The g(z) and g(x) factors as functions of the k(z), radius R and length L are calculated for the wires and rods, respectively. For the wires, the g(z) of the electron ground state increases, and the g(z) of the hole ground state decreases first, then increases with the k(z) increasing. For the rods, the g(z) and g(x) of the electron ground state decrease as the R or the L increases. The g(x) of the hole ground state decreases, the g(z) of the hole ground state increases with the L increasing. The variation of the g(z) of the wires with the k(z) is in agreement with the variation of the g(z) of the rods with the L.

Energy bands and acceptor binding energies of GaN

The energy bands of zinc-blende and wurtzite GaN are calculated with the empirical pseudopotential method, and the pseudopotential parameters for Ga and N atoms are-given. The calculated energy bands are in agreement with those obtained by the ab initio method. The effective-mass theory for the semiconductors of wurtzite structure is established, and the effective-mass parameters of GaN for both structures are given The binding energies of acceptor states are calculated by solving strictly the effective-mass equations. The binding energies of donor and acceptor are 24 and 142 meV for the zinc-blende structure, 20 and 131, and 97 meV for the wurtzite structure, respectively, which are consistent with recent experimental results. It is proposed that there are two kinds of acceptor in wurtzite GaN. One kind is the general acceptor such as C, which substitutes N, which satisfies the effective-mass theory. The other kind of acceptor includes Mg, Zn, Cd, etc., the binding energy of these accepters is deviated from that given by the effective mass theory. In this report, wurtzite GaN is grown by the molecular-beam epitaxy method, and the photoluminescence spectra were measured. Three main peaks are assigned to the donor-acceptor transitions from two kinds of accepters. Some of the transitions were identified as coming from the cubic phase of GaN, which appears randomly within the predominantly hexagonal material. [S0163-1829(99)15915-0].

Low threading-dislocation-density Ge film on Si grown on a pitting Ge buffer layer

A Ge layer with a pitting surface can be obtained when the growth temperature is lowered to 290 degrees C. On the low temperature Ge buffer layer with pits, high quality Ge layer was grown at 600 degrees C with a threading dislocation density of similar to 1x10(5)cm(-2). According to channeling and random Rutherford backscattering spectrometry spectra, a chi(min) value of 10% and 3.9% was found, respectively, at the Ge/Si interface and immediately under the surface peak. The root-mean-square surface roughness of Ge film was 0.33nm.

A 5GHz low power WLAN transceiver SiGe RFIC for personal communication terminal applications

A low-cost low-power single chip WLAN 802.11a transceiver is designed for personal communication terminal and local multimedia data transmission. It has less than 130mA current dissipation, maximal 67dB gain and can be programmed to be 20dB minimal gain. The receiver system noise figure is 6.4dB in hige-gain mode.

基于素数序列的Java哈希表性能优化

分析了Java哈希表的实现特点并给出了导致其性能恶化的一种数据模式.针对这种数据模式的特点,提出了基于素数序列的哈希表优化方法,从而几乎完全避免了该模式下哈希表的性能恶化.实验与理论结果表明:对提出的模式数据,优化方法产生的Hash碰撞比JDK中的方法下降接近100%,而且对随机数据下的Java哈希表性能也有改善.

卫星网络计算任务调度技术研究

卫星网络是一个由不同轨道上多种类型的卫星组成的系统，按照空间信息资源的最大有效综合利用原则，互通互连、有机构成的智能化体系。随着这种新型网络系统的产生和应用，卫星自身的功能越来越强大，卫星网络的资源越来越丰富。合理的任务调度体系结构和高效的任务调度算法可以给卫星网络的使用带来两方的好处：一方面可以将各种网络资源有机的整合在一起以实现计算，存储和网络等资源的共享和协同工作，取得较高的系统资源利用率；另一方面，能够支持多样化的应用类型，对各种任务进行高效地调度，取得更好的作业执行效率，为用户提供更好的服务。 本文针对卫星网络，首先分析了卫星网络及各种相关应用的特点，然后对当前被广泛应用于网格的任务调度技术进行了深入调研，通过对卫星网络和网格系统各种特点的对比和分析，提出一种能够适应卫星网络特点的任务调度体系结构，并基于该体系结构设计了任务调度算法。借助仿真工具对设计出的任务调度算法和一些常用的任务调度算法进行了仿真和性能比较，仿真结果表明，设计的任务调度算法能够取得更好的调度性能，在卫星网络环境中可以高效地工作。

基于Rete算法的多Agent的实时协同推理

1 引言多Agent系统是由若干具有一个或多个目标的Agent按照一定的信息关系和控制关系以及问题求解能力的分布模式组成的系统,它主要研究一组在逻辑上或物理上分离的Agent之间行为的协调。目前,多Agent系统已应用于诸如空中交通控制、电子商务、通讯网络管理和作业调度等生产实际领域。Agent技术应用到实际领域时映射的对象一般有