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arXiv 1902.06314cond-mat.mtrl-sci
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立方硼砷化物中由化学计量关联的化学势引起的本征点缺陷

Native point defects from stoichiometry-linked chemical potentials in cubic boron arsenide

Yaxian Wang, Wolfgang Windl

摘要:

点缺陷的存在通常会破坏半导体中的化学计量。例如,AB化合物中A位上的空位使晶体富含B。当化学计量比改变时,化学势也改变。虽然流行的第一性原理方法提供了显着的洞察点缺陷的特点,在一个透明的方式,晶体化学计量和化学势之间的关键联系,通常没有。然而,对化学势的特别选择可能导致在某些费米能级范围内的非物理负形成能,以及电荷平衡的问题。在这里,我们制定了一个规范的框架,描述了每个元素的化学势是如何直接链接到(非)化学计量条件下的晶体的组成,而不是特设假设的化学势是在一定的生长条件下的元素限制。因此,在带隙内化学势随费米能级变化,形成能为正。使用这样的方法,我们目前的$ab$ $initio$的结果,本征点缺陷的BA,具有超高的室温热导率的半导体。我们发现,反位是非化学计量比材料的本构缺陷,而B $_\mathrm{As}$反位和B空位占主导地位的化学计量比材料。我们进一步讨论的热力学平衡和电荷中性点的BAs根据我们的化学计量确定的化学势。如前所述,我们的工作提供了一种更适用和更容易获得的方法来解决半导体中的缺陷形成能,特别是那些通常看到负形成能的宽禁带半导体。

英文摘要:

The presence of a point defect typically breaks the stoichiometry in a semiconductor. For example, a vacancy on an A-site in an AB compound makes the crystal B-rich. As the stoichiometry changes, so do the chemical potentials. While the prevalent first-principles methods have provided significant insight into characters of point defects in a transparent manner, the crucial connection between crystal stoichiometry and chemical potentials is usually not made. However, ad hoc choices for chemical potentials can lead to nonphysical negative formation energies in some Fermi level ranges, along with questions about charge balance. Herein, we formulate a canonical framework describing how the chemical potential of each element is directly linked to the composition of the crystal under (off-)stoichiometric conditions instead of the ad hoc assumption that the chemical potential is the elemental limit under a certain growth condition. Consequently, the chemical potential changes with the Fermi level within the band gap, and the formation energies are positive. Using such an approach, we present $ab$ $initio$ results for native point defects in BAs, a semiconductor with ultra-high room temperature thermal conductivity. We find that antisites are the constitutional defects in off-stoichiometric material, while B$_\mathrm{As}$ antisites and B vacancies dominate in the stoichiometric material. We further discuss the thermodynamic equilibrium and charge neutrality point in BAs in light of our stoichiometry-determined chemical potentials. As discussed, our work offers a more applicable and accessible approach to tackle defect formation energies in semiconductors, especially the ones with wide gap where negative formation energies are commonly seen.

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