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Modeling nitride based quantum dots: Multimillion atom tight-binding simulations.

机译：基于氮化物的量子点建模：数百万个原子紧密结合模拟。

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摘要

The theoretical calculation of the electronic structure of any constituent materials is the first step towards the interpretation and understanding of the experimental data and reliable device design. This is essentially true for nanoscale devices where the atomistic granularity of the underlying materials and the quantum mechanical nature of charge carriers play critical role in determining the overall device performance. In this work, within a fully atomistic and quantum-mechanical framework, we investigate the electronic structure of wurtzite InN quantum dots (QDs) self-assembled on GaN substrate. The main objectives are three-fold -- (1) to explore the nature and the role of crystal atomicity, strain-field, piezoelectric and pyroelectric potentials in determining the energy spectrum and the wavefunctions, (2) to address the redshift in the ground state, the symmetry-lowering and the non-degeneracy in the first excited state, and the strong band-mixing in the overall conduction band electronic states, a group of inter-related phenomena that has been revealed in recent spectroscopic analyses, and (3) to study the size-dependence of the above mentioned phenomena and the electronic states as a whole. We also demonstrate the importance of three-dimensional (3-D) atomistic material representation, and the need for using realistically-extended substrate and cap layers (multimillion atom modeling) in studying the built-in structural and electric fields in these reduced-dimensional QDs. Models used in this study are as follow: (1) VFF Keating model for atomistic strain relaxation;(2) 20-band nearest-neighbor sp3d5s* tight-binding model for the calculation of single-particle energy states; and (3) microscopically determined polarization constants in conjunction with an atomistic 3-D Poisson solver for the calculation of the piezo- and the pyro-electricity.
机译：任何构成材料的电子结构的理论计算是朝着解释和理解实验数据和可靠的器件设计的第一步。对于底层器件的原子粒度和电荷载流子的量子力学性质在决定整体器件性能方面起关键作用的纳米级器件，这基本上是正确的。在这项工作中，我们在一个完全原子化和量子力学的框架内，研究了自组装在GaN衬底上的纤锌矿InN量子点（QD）的电子结构。主要目标是三个方面-（1）探讨晶体原子性，应变场，压电和热电势在确定能谱和波函数方面的性质和作用，（2）解决地面的红移态，第一激发态的对称性降低和非简并，以及整个导带电子态中的强谱带混合，最近光谱分析中发现的一组相互关联的现象，以及（3 ）研究上述现象与整个电子状态的大小相关性。我们还演示了三维（3-D）原子材料表示的重要性，以及在研究这些缩减尺寸的内置结构和电场中使用逼真的扩展衬底和盖层（数百万个原子模型）的必要性QD。本研究中使用的模型如下：（1）用于原子应变松弛的VFF基廷模型；（2）用于计算单粒子能量态的20能带最近邻sp3d5s *紧束缚模型； （3）与原子3D泊松解算器结合使用显微镜确定的极化常数，用于计算压电和热电。

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  • 作者

    Mohammed, Shareef uddin.;

  • 作者单位

    Southern Illinois University at Carbondale.;

  • 授予单位 Southern Illinois University at Carbondale.;
  • 学科 Engineering Electronics and Electrical.;Nanoscience.
  • 学位 M.S.
  • 年度 2009
  • 页码 58 p.
  • 总页数 58
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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