Bridging the gap between atomic microstructure and electronic properties of alloys: The case of (In,Ga)N
Bridging the gap between atomic microstructure and electronic properties of alloys: The case of (In,Ga)N
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弥合合金原子微观结构和电子性能之间的差距：(In,Ga)N 的案例
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
A. Zunger
中科院分区：
文献类型：
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作者：
J. A. Chan;Jefferson Z. Liu;A. Zunger
合金的原子微观结构很少是完全随机的，而是表现出不同形状的沉淀物、簇、锯齿链等。虽然预计这种微观结构特征将影响电子结构载流子定位和带隙，但迄今为止，理论研究仅限于研究完全随机或人工“猜测”的微观结构特征。在本文中，我们使用静态蒙特卡罗方法模拟热力学平衡中的合金微观结构，并使用赝势超晶胞方法明确地研究其电子结构。通过这种方式，我们可以将原子微观结构与其电子特性联系起来。我们使用密度泛函理论和 50 个有序结构的总能量推导出 InGaN 的原子微观结构，以构建 ii 多体团簇展开，包括我们应用了 iii 对由 27000 多个原子组成的系统进行静态蒙特卡罗模拟以确定平衡原子微观结构的应变效应。我们研究了两种类型的合金热力学行为：a在晶格非共格条件下，生成热函为正，因此合金体系在混溶间隙温度TMG以下发生相分离，b在晶格相干条件下，生成热函可以为负，因此合金体系表现出有序倾向。微观结构根据结构图案进行分析，例如锯齿形链和 InnGa4−nN 四面体簇。利用经验赝势法计算出相应的电子结构，并从带边能量和波函数局域化方面进行了分析。我们发现无序合金没有电子局域化，但有显着的空穴局域化，而在非相干条件下低于混溶间隙，富In沉淀物导致强烈的电子和空穴局域化以及带隙减小。
The atomic microstructure of alloys is rarely perfectly random, instead exhibiting differently shaped precipitates, clusters, zigzag chains, etc. While it is expected that such microstructural features will affect the electronic structures carrier localization and band gaps , theoretical studies have, until now, been restricted to investigate either perfectly random or artificial “guessed” microstructural features. In this paper, we simulate the alloy microstructures in thermodynamic equilibrium using the static Monte Carlo method and study their electronic structures explicitly using a pseudopotential supercell approach. In this way, we can bridge atomic microstructures with their electronic properties. We derive the atomic microstructures of InGaN using i density-functional theory total energies of 50 ordered structures to construct a ii multibody cluster expansion, including strain effects to which we have applied iii static Monte Carlo simulations of systems consisting of over 27000 atoms to determine the equilibrium atomic microstructures. We study two types of alloy thermodynamic behavior: a under lattice incoherent conditions, the formation enthalpies are positive and thus the alloy system phase-separates below the miscibility-gap temperature TMG, b under lattice coherent conditions, the formation enthalpies can be negative and thus the alloy system exhibits ordering tendency. The microstructure is analyzed in terms of structural motifs e.g., zigzag chains and InnGa4−nN tetrahedral clusters . The corresponding electronic structure, calculated with the empirical pseudopotentials method, is analyzed in terms of band-edge energies and wave-function localization. We find that the disordered alloys have no electronic localization but significant hole localization, while below the miscibility gap under the incoherent conditions, In-rich precipitates lead to strong electron and hole localization and a reduction in the band gap.