共查询到18条相似文献,搜索用时 93 毫秒
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高分辨率X射线衍射技术被用来分析基于InP衬底的应变的InGaAs和InAlAs单层材料和应变补偿的InGaAs/InAlAs超晶格材料.通过倒空间mapping得到的单层材料的错向角大约为10-3度,可以忽略不计.通过摇摆曲线得到了单层材料的组分和体失配度,接着单层材料的结果被用来分析在相同的条件下利用MBE技术生长的超晶格材料.利用倒空间mapping精确得到了超晶格的平均垂直失配度和各层的厚度,通过X射线模拟软件得到的超晶格材料的模拟曲线和实测曲线吻合的很好. 相似文献
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本文采用计算超晶格电子态常用的Kronig-Penney模型和形变势理论,从理论上探讨了GaInNAs/GaAs超晶格能带系统的能带结构,计算得到了能带结构随各亚层参量变化的一般性规律、超晶格的能量色散关系、应变造成的影响以及不同亚层厚度的系统禁带宽度。计算了超晶格的阱层材料在不同的组分选择下,GaInAsN/GaAs超晶格吸收带边为1eV的超晶格相关参数的对应关系以及超晶格应变状态。计算表明采用高In低N的GaInNAs材料作为GaInNAs/GaAs超晶格的阱层时更有利于获得高质量且较厚的GaInNAs/GaAs超晶格有源区,并且此时可以获得较好的应变补偿;进一步对超晶格太阳能电池的内量子效率进行了模拟计算,分析了1eV吸收带边GaInAsN/GaAs超晶格太阳能电池对提高整体光电转换效率的可行性。 相似文献
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通过在多层量子点体系中引入应变补偿层,改变量子点系统的应力场分布,可以控制生长过程中量子点的大小均匀性和密度,最终获得高质量、高密度的多层量子点体系,应用到量子点光电器件中,可改善器件的电学和光学性能。介绍了应变补偿层在量子点体系中作用的原理,常用的应变补偿材料体系,以及目前国内外对应变补偿技术的研究状况,最后提出了现存的问题和今后的发展方向。 相似文献
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三、应变超晶格材料以前研究超晶格材料时,除了AlGaAs/GaAs系以外,对其他物质结合而形成超晶格的研究工作不很积极,原因是它们之间的晶格常数不同,会引起薄膜之间产生失配位错而得不到良好质量的晶体。但是,如果多层薄膜的厚度十分薄时,在晶体生长时反而不怎么产生缺陷,也就是在弹性形变限度之内的超薄膜中,晶格本身发生应变而消除缺陷的产生。巧妙地利用这种性质,目前开始研究晶格常数不同材料形成的应变超晶格的制备。在应变超晶格中发现了一般超晶格中没有的新特性。这讲将对应变超晶格的设计理论和研究动向进行介绍。 相似文献
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本文研究了SiO2和Si层的厚度分别为2-8nm和1.5-3nm的Si/SiO2超晶格在交流电场下的电致发光特性。以超晶格中SiO2层内加速的过热电子碰撞激发纳米Si层中密集的硅量子点,获得了Si/SiO2超晶格蓝绿色交流电致发光。Si/SiO2超晶格的电致发光亮度随电压升高呈现指数增强,最高发光亮度可达到1.4cd/m2。随着Si层厚度的增加,Si/SiO2超晶格电致发光谱的低能侧发光峰相对增强,可以归结为纳米Si层厚度对其中硅量子点尺寸分布的限制作用。当超晶格中SiO2层厚度小于过热电子的平均自由程时,过热电子的平均能量减小导致短波侧的发光强度迅速下降,电致发光强度随之迅速降低。 相似文献
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《Materials Science and Engineering: B》2002,88(2-3):143-152
Self-organized vertical and lateral ordering in self-assembled quantum dot superlattices is based on long-range elastic interactions between the growing dots on the surface and those buried in the previous superlattice layers. These interactions may lead to a correlated dot nucleation and to the formation of ordered superstructures. For various materials systems different types of structures may be formed, ranging from vertically aligned dot superlattices for Si–Ge or III–V semiconductors to an fcc-like ABCABC… stacking in IV–VI materials. These differences are caused by the given elastic anisotropy of the superlattice materials. From systematic theoretical calculations, for all materials with high elastic anisotropy and growth orientations parallel to an elastically soft direction, layer-to-layer dot correlations inclined to the growth direction may be formed. Further changes in the dot correlations are caused by the modification of the elastic strain fields by the finite extent and shape of the buried islands. This is illustrated for IV–VI PbSe/PbEuTe dot superlattices, where either vertically aligned or fcc-stacked dot arrangements are formed as a function of spacer thickness. 相似文献
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Povolotskyi M. Di Carlo A. Lugli P. Birner S. Vogl P. 《Nanotechnology, IEEE Transactions on》2004,3(1):124-128
We theoretically investigated the elastic deformation and piezoelectric field in InAs quantum dots grown on (N11) GaAs substrates. Particular attention was given to the influence of the substrate orientation on both the volume deformation of the dot and the strain-induced piezoelectric field. The piezoelectric effects are enhanced by the lower symmetry growth directions. The influence of the piezoelectric fields on the electron and hole ground states for a (N11) quantum dot was also investigated within the effective mass approximation. We find a significant dependence of the fundamental transition energy on the polarity of the substrate's surface. 相似文献
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采用LP-MOVPE技术,在(001)InP衬底上生长的InAs/InP自组装量子点是无序的。为了解决这个问题,在InP衬底上先生长张应变的GaAs层,然后再生长InAs层,可得到有序化排列的量子点。本文对张应变GaAs层引入使量子点有序化排列的机理进行了分析,为生长有序化、高密度,均匀性好自组装量子点提供了依据。 相似文献
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Yen-Sheng Lin 《Journal of Materials Science》2006,41(10):2953-2958
The formation of In-rich quantum dot structures will induce strain energy in the quantum well layer, forming the clusters
and stacking faults influencing the optical properties. Our results showed different QW widths with the formation of various
In-rich quantum dot structures and different levels of strain energy. Upon thermal annealing, energy relaxation resulted in
the reshaping of quantum dots and hence the changes of optical properties. The results of temperature variations of PL spectral
peak, integrated PL intensity and PL decay time showed consistent trends in varying strain energy distribution. 相似文献
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We have investigated the effect of post-growth rapid thermal annealing on self-assembled InAs/GaAs bilayer quantum dot samples having very thin barrier thickness (7.5-8.5 nm). In/Ga interdiffusion in the samples due to annealing is presumed to be controlled by the vertical strain coupling from the seed dots in bilayer heterostructure. Strain coupling from embedded seed QD layer maintains a strain relaxed state in active top islands of the bilayer quantum dot sample grown with comparatively thick spacer layer (8.5 nm). This results in minimum In/Ga interdiffusion. However controlled interdiffusion across the interface between dots and GaAs barrier, noticeably enhances the emission efficiency in such bilayer quantum dot heterostructure on annealing up to 700 °C. 相似文献
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We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs(100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed. 相似文献
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Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. 相似文献