Zeng Hui, Wu Meng, Gao Haixia, Wang Yuansheng, Xu Hongfei, Cheng Meijuan, Lin Qiubao
College of Science, Hunan University of Science and Engineering, Yongzhou 425199, China.
College of Materials Science and Engineering, Hunan University, Changsha 410082, China.
Materials (Basel). 2023 Oct 19;16(20):6758. doi: 10.3390/ma16206758.
Iron impurities are believed to act as deep acceptors that can compensate for the n-type conductivity in as-grown GaO, but several scientific issues, such as the site occupation of the Fe heteroatom and the complexes of Fe-doped β-GaO with native defects, are still lacking. In this paper, based on first-principle density functional theory calculations with the generalized gradient approximation approach, the controversy regarding the preferential Fe incorporation on the Ga site in the β-GaO crystal has been addressed, and our result demonstrates that Fe dopant is energetically favored on the octahedrally coordinated Ga site. The structural stabilities are confirmed by the formation energy calculations, the phonon dispersion relationships, and the strain-dependent analyses. The thermodynamic transition level Fe/Fe is located at 0.52 eV below the conduction band minimum, which is consistent with Ingebrigtsen's theoretical conclusion, but slightly smaller than some experimental values between 0.78 eV and 1.2 eV. In order to provide direct guidance for material synthesis and property design in Fe-doped β-GaO, the defect formation energies, charge transitional levels, and optical properties of the defective complexes with different kinds of native defects are investigated. Our results show that V and O can be easily formed for the Fe-doped β-GaO crystals under O-rich conditions, where the +3 charge state FeGa and -2 charge state FeO are energetically favorable when the Fermi level approaches the valence and conduction band edges, respectively. Optical absorption shows that the complexes of FeGa and FeV can significantly enhance the optical absorption in the visible-infrared region, while the energy-loss function in the β-GaO material is almost negligible after the extra introduction of various intrinsic defects.
铁杂质被认为作为深受主，可补偿生长态GaO中的n型导电性，但仍存在一些科学问题，如Fe杂原子的占位以及Fe掺杂的β-GaO与本征缺陷的复合体等问题仍未得到解决。本文基于采用广义梯度近似方法的第一性原理密度泛函理论计算，解决了β-GaO晶体中Fe优先掺入Ga位的争议，我们的结果表明，Fe掺杂剂在八面体配位的Ga位上在能量上更有利。通过形成能计算、声子色散关系和应变相关分析证实了结构稳定性。热力学转变能级Fe/Fe位于导带最小值以下0.52 eV处，这与英格布里格森的理论结论一致，但略小于0.78 eV至1.2 eV之间的一些实验值。为了为Fe掺杂β-GaO的材料合成和性能设计提供直接指导，研究了具有不同本征缺陷的缺陷复合体的缺陷形成能、电荷跃迁能级和光学性质。我们的结果表明，在富氧条件下，Fe掺杂的β-GaO晶体容易形成V和O，当费米能级分别接近价带和导带边缘时，+3电荷态的FeGa和-2电荷态的FeO在能量上更有利。光吸收表明，FeGa和FeV的复合体可以显著增强可见光-红外区域的光吸收，而在额外引入各种本征缺陷后，β-GaO材料中的能量损失函数几乎可以忽略不计。
