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Plasma assisted molecular beam epitaxial growth of GaN with low growth rates and their properties
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A systematic investigation on PA-MBE grown GaN with low growth rates(less than 0.2μm/h)has been conducted in a wide growth temperature range,in order to guide future growth of sophisticated fine structures for quantum device applications.Similar to usual growths with higher growth rates,three growth regions have been revealed,namely,Ga droplets,slightly Ga-rich and N-rich 3D growth regions.The slightly Ga-rich region is preferred,in which GaN epilayers demonstrate optimal crystalline quality,which has been demonstrated by streaky RHEED patterns,atomic smooth surface morphology,and very low defect related yellow and blue luminescence bands.The growth temperature is a critical parameter to obtain high quality materials and the optimal growth temperature window(~700-760℃)has been identified.The growth rate shows a strong dependence on growth temperatures in the optimal temperature window,and attention must be paid when growing fine structures at a low growth rate.Mg and Si doped GaN were also studied,and both p-and n-type materials were obtained. 相似文献
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为了研究了载流子驰豫时间和逃逸时间对量子点激光器的阈值电流、外微分量子效率的影响,分析了载流子在S-K自组织量子点激光器结构中捕获、逃逸过程,建立速率方程并在稳态下求解.结果表明,驰豫时间越长,量子点基态载流子数量越少,转换为光子的数量就越少,量子点激光器的阈值电流就越大,外微分量子效率就越小;而载流子从量子点基态的逃逸到盖层的时间越长,量子点激光器的阈值电流就越小,外微分量子效率就越大. 相似文献
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为了得到二氧化钛反蛋白石光子晶体中影响光子定域化的规律,基于Mie散射理论和低浓度近似,对光子定域化参量进行了数值计算与理论分析,发现在该氧化物的剩余射线区内,入射波长和散射体大小对光子定域化有明显的影响.结果表明,在散射体浓度为10%,相对折射率大于3.8时,在中红外区13.3~15.3 μm范围内出现了光子定域化现... 相似文献
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中性top-pion在高能正负电子对撞机上的产生@岳崇兴$河南师范大学物理与信息工程学院!河南新乡,453002
@徐庆君$河南师范大学物理与信息工程学院!河南新乡,453002&&&& 相似文献
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Structural characterization of Al_(0.55)Ga_(0.45)N epitaxial layer determined by high resolution x-ray diffraction and transmission electron microscopy
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Structural characteristics of Alo.55 Gao.45N epilayer were investigated by high resolution x-ray diffraction(HRXRD)and transmission electron microscopy(TEM);the epilayer was grown on GaN/sapphire substrates using a high-temperature A1 N interlayer by metal organic chemical vapor deposition technique.The mosaic characteristics including tilt,twist,heterogeneous strain,and correlation lengths were extracted by symmetric and asymmetric XRD rocking curves as well as reciprocal space map(RSM).According to Williamson-Hall plots,the vertical coherence length of AlGaN epilayer was calculated,which is consistent with the thickness of AlGaN layer measured by cross section TEM.Besides,the lateral coherence length was determined from RSM as well.Deducing from the tilt and twist results,the screw-type and edge-type dislocation densities are 1.0×10~8 cm~(-2) and 1.8×10~(10) cm~(-2),which agree with the results observed from TEM. 相似文献
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讨论了同时利用中国的暗物质直接探测实验CDEX和PandaX靶核的反冲能量数据及相关的线上数据分析系统AMIDAS重建暗物质粒子的质量和一维速度分布函数的可行性.结果表明:结合CDEX和Pan—daX未来的实验数据,对于较轻的暗物质粒子(质量约小于175OeV),AMIDAS可以很好地重建其质量. 相似文献
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TC2 (topcolor- assisted technicolor)理论在提供动力学破缺机制的同时 ,产生了足够重的顶夸克质量 ,克服了传统人工色理论的缺点 ,是目前人们比较感兴趣的一类新物理模型。此类模型预言了一个色单态规范玻色子 Z′的存在。此规范玻色子的存在可视为 TC2理论的主要特征之一。在标准模型中 ,轻子味改变过程的衰变几率非常小 ,且最近的高能实验亦给出了强烈限制。比如μ轻子味改变衰变过程μ→ 3e,μ→ eγ以及μ→ eγγ的实验要求其分支比为 :Br(μ→ 3e) 1 0 -12 ,Br(μ→ eγ) 4.9× 1 0 -11,Br(μ→ eγγ) 1 0 -10。显然这些最新… 相似文献