Strain and photoluminescence characterization of cubic (In,Ga)N films grown on GaAs(001) substrates

Cubic InxGa1-xN films were successfully grown on GaAs(001) substrates by metalorganic chemical-vapor deposition. The values of x content ranging from 0.10 to 0.24 obtained at different growth conditions were measured by double-crystal x-ray diffraction (XRD). The perpendicular and parallel elastic strain of the In0.2Ga0.8N layer, epsilon(perpendicular to)=0.4% and epsilon(parallel to)=-0.4% for GaN and epsilon(perpendicular to)=0.37% and epsilon(parallel to)=-0.37% for InGaN, respectively, were derived using the XRD measurements. The inhomogeneous strain and the average grain size of the In0.2Ga0.8N/GaN films were also studied by XRD. Photoluminescence spectra were used to measure the optical characterization of the InxGa1-xN thin films with different In composition, and the near-band-edge emission dependence of cubic InxGa1-xN on the x value is nearly linear with In content x less than or equal to 0.24. (C) 2000 American Institute of Physics. [S0021-8979(00)03908-6].

A novel 1.3-mu m high T-0 AlGaInAs/InP strained-compensated multi-quantum well complex-coupled distributed feedback laser diode

A 1.3-mu m AlGaInAs/InP buried heterostructure (BH) stripe distributed feedback laser with a novel AlInAs/InP complex-coupled grating grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) is proposed and demonstrated. A high characteristic temperature (T-0 = 90K between 20-80 degrees C) and temperature-insensitive slope efficiency (0.25 dB drop from 20 to 80 degrees C) in 1.3 mu m AlGaInAs/InP DFB lasers was obtained by introducing AI(Ga)InAs graded-index separate-confinement heterostructure (GRINSCH) layers and a strained-compensated (SC) multi-quantum well (MQW).

Lateral ordered InGaAs self-organized quantum dots grown on (311) GaAs by conventional molecular beam epitaxy

Self-assembled InxGa1-xAs quantum dots (QDs) on (311) and (100) GaAs surfaces have been grown by conventional solid source molecular beam epitaxy. Spontaneously ordering alignment of InxGa1-xAs QDs with lower In content around 0.3 has been observed on As-terminated (B type) surfaces. The direction of alignment orientation of the QDs formation differs from the direction of misorientation of the (311) B surface, and is strongly dependent upon the In content x. The ordering alignment becomes significantly deteriorated as the In content is increased to above 0.5 or as the QDs are formed on (100) and (311) Ga-terminated (A type) substrates.

Normal-incidence intersubband (In, Ga)As/GaAs quantum dot infrared photodetectors

We report the device performance of normal-incidence (In, Ga)As/GaAs quantum dot intersubband infrared photodetectors. A primary intersubband transition peak is observed at the wavelength of 13 mu m (E-0 --> E-1) and a secondary peak at 11 mu m (E-0 --> E-2). The measured energy spacing in the conduction band of the quantum dots is in good agreement with low temperature photoluminescence measurement and calculations. A peak detectivity of 1 x 10(10) cm Hz(1/2)/W at 13 mu m was achieved at 40 K for these devices. (C) 1998 American Institute of Physics. [S0003-6951(98)01440-5].

Tunneling magnetoresistance in (Ga,Mn)As/Al-O/CoFeB hybrid structures

Tunneling magnetoresistance (TMR) in Ga(0.9)2Mn(0.08)As/Al-O/Co40Fe40B20 trilayer hybrid structure as a function of temperature from 10 to 50 K with magnetic field vertical bar H vertical bar <= 2000 Oe has been studied. TMR ratio of 1.6% at low fields at 10 K was achieved with the applied current of 1 mu A. The behavior of junction resistance was well explained by the tunneling resistance across the barrier. Strong bias dependences of magnetoresistance and junction resistance were presented. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3068418]

MVPE Ga 掺杂ZnO 薄膜材料的制备及其在LED 中的应用

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Temperature dependent photoluminescence of an In(Ga)As/GaAs quantum dot system with different areal density

We have systematically studied the temperature dependent photoluminescence of a self-assembled In(Ga)As/GaAs quantum dot (QD) system with different areal densities from similar to 10(9) to similar to 10(11) cm(-2). Different carrier channels are revealed experimentally and confirmed theoretically via a modified carrier equation model considering a new carrier transfer channel, i.e. continuum states ( CS). The wetting layer is demonstrated to be the carrier quenching channel for the low-density QDs but the carrier transfer channel for the high-density QDs. In particular, for the InGaAs/GaAs QDs with a medium density of similar to 10(10) cm(-2), the CS is verified to be an additional carrier transfer channel in the low temperature regime of 10-60 K, which is studied in detail via our models. The possible carrier channels that act on different temperature regimes are further discussed, and it is demonstrated that density is not a crucial factor in determining the carrier lateral coupling strength.

一种基于Messy GA的结构测试数据自动生成方法

结构性测试是标识测试用例的基本方法之一．由于程序语言的复杂性以及被测程序的多样性，自动生成结构测试数据的一种有效方法是根据程序运行结果指导生成过程，通过不断迭代，生成符合要求的测试数据集．提出一种基于Messy GA的结构测试数据自动生成方法，将测试覆盖率表示为测试输入集X的函数F（X），并利用Messy GA不需要染色体模式排列的先验知识即可进行优化求解的性质对F（X）的进行迭代寻优，进一步提高了搜索的并行性，并最终提高测试覆盖率．对一组标准测试程序和若干实际应用程序的实验结果表明，较之现有基于遗传算法的生成方法，该方法能够以更高的效率生成更高质量的测试数据，并适用于较大规模的程序．

黄土高原长期种植苜蓿对土壤硫、钙、镁的影响

以22年定位试验为基础,研究黄土高原长期种植紫花苜蓿(Medicago sativaL.)情况下土壤硫、钙、镁组分的变化。结果表明:长期施P使苜蓿连作耕层土壤总硫、有效硫、水溶性硫、吸附性硫、HCl可溶性硫、总无机硫和有机硫含量分别增加9.41%、62.41%、47.51%、30.07%、2.25%、5.38%和17.54%;长期施NPM使苜蓿连作耕层土壤总硫、有效硫、水溶性硫、吸附性硫、HCl可溶性硫、总无机硫和有机硫含量分别增加20.89%、98.31%、68.44%、57.34%、8.07%、12.54%和37.69%。长期施P使苜蓿连作耕层土壤全钙、有效钙、水溶态钙、交换态钙和酸溶态钙含量增加分别增加4.64%、4.27%、11.66%、4.05%和8.59%,但残余态钙含量降低2.21%;长期施NPM使苜蓿连作耕层土壤全钙、有效钙、水溶态钙、交换态钙和酸溶态钙含量增加分别增加8.69%、8.30%、51.59%、6.73%和27.77%,但残余态钙含量降低26.23%。长期施NPM使苜蓿连作耕层土壤全镁、有效镁、水溶态镁、交换态镁、酸溶态镁和残余态镁含量分别增加7.38%、61.98%、63.16%...

新型土壤改良剂对夏玉米生理生长特性的影响

通过大田玉米试验,验证新型土壤改良剂对夏玉米生育期土壤水分、紧实度及玉米生理生长特性的影响。结果表明,施用改良剂PJG和PFL夏玉米全生育期平均株高、叶面积分别高于对照20.7%、19.75%和51.88%、72.37%;2种改良剂对干物质积累的影响存在差异,影响效果依次为茎干重>叶干重>根干重。夏玉米光合速率和叶绿素含量受土壤改良剂影响较大,PJG和PFL分别高于对照29.96%、24.48%和73.36%、68.53%。在0~10 cm土层内,施用PJG和PFL后土壤紧实度分别低于对照44.44%和42.91%。施用改良剂PJG后,0~20 cm土层土壤含水量维持在田间持水量的77.9%左右,未施用改良剂土壤,夏玉米生育期表层土壤含水量起伏变化较大。土壤改良剂PJG在夏玉米的施用效果略好于PFL。

PET的结晶动态力学性能及成核剂的研究

利用DDV-II-EA型全自动粘弹谱仪考察了不同PET样品等温和升温过程中动态力学量的变化。得到了等温结晶过程中PET复合模量随时间变化的定量表达式，即在结晶诱导期内复合模量随时间缓慢而线性增长；主结晶期内，复合模量的对数随时间的变化符合Avrami方程；次级结晶期内。复合模量随时间对数而线性增长。对等速升温过程，非晶样品的结晶和玻璃化转变都将引起复合模量的急剧变化，并形成损耗模时峰。但在结晶过程中得合模量由小变大，由耗因子峰tanδmax出现于损耗模量峰E''_(max)之前，损耗模量峰高度随频率升高而显升高，而峰出现的温度与频率无关；这与玻璃化转变出现时复合损耗与损耗模量的变化相反。利用玻璃化转变损耗随结晶度和频率变化的关系及大分子运动模型对上述结果做了定性说明。考察了动态力学方法在表征样品冷结晶能力、获取结晶动力学参数及研究结晶诱导期和次级结晶过程中聚合物状态变化方面的作用；通过与PET结晶过程中介电参量变化的对比，推得介电常数随模量的对数或结晶度的增加而线性减小。利用DSC及线膨胀方法，考察了多种添加剂对PET结晶能力的影响，从中选择了几种代表不同种类并对PET结晶具有明显促进作用的添加剂加入PET，对其多项性能进行了考察。结果表明，苯甲酸钠、硬脂酸钠、氢氧化铝对PET冷结晶和熔体结晶能力自有很强的促进作用，并使结晶含量有所提高，但它们使PET分子明显降解，生成小分子量的组分，对非晶PET起增塑作用或直接引发结晶；滑石粉、二氧化硅、碳酸钙对PET熔体结晶有明显的促进作用，对PET热膨胀性质、动态力学性质及介电性质不产生明显影响，也不降低PET分子量，但对冷结晶只有较弱的促进作用；5-10wt%的增塑剂能明显提高PET冷结晶能力，但基本不影响PET熔体结晶能力，并使PET软化温度降低，热膨胀系数变大；添加剂含量增加，能使PET结晶能力增强。但对大部分添加剂，含量在0.5-wt%之内时，这种变化很明显，含量大于1-wt%时，变化很小。总含量一定时，双组份添加剂对PET结晶的促进作用基本上介于二单组份之间。添加剂的加入，还有使PET结晶有序性增加的趋势，使非晶样品活化能增大。对上述变化的部分机理进行了探讨。