Point defects in p-type transparent conductive CuMO2 (M = Al, Ga, In) from first principles
Point defects in p-type transparent conductive CuMO2 (M = Al, Ga, In) from first principles
复制标题
DOI：
10.1103/physrevmaterials.5.104602
复制
发表时间：
2021-10-08
影响因子：
3.4
通讯作者：
Oba, Fumiyasu
中科院分区：
文献类型：
--
作者：
Gake, Tomoya;Kumagai, Yu;Oba, Fumiyasu
采用基于Heyd-Scuseria-Ernzerhof （HSE06）混合泛函数方法的第一性原理计算方法研究了delafote CuMO2 （M = Al, Ga, in）中的原生点缺陷。所有体系中的Cu空位均表现出较低的形成能和较浅的受体能级，这主要有助于p型电导率的形成。在受控生长条件下，供体型天然缺陷的空穴补偿并不能完全限制所有CuMO2中p型掺杂。相比之下，在CuAlO2和CuGaO2中，受体型天然缺陷，特别是Cu空位，在高费米能级位置表现出低甚至负的形成能，从而补偿载流子电子，限制了n型掺杂。在CuMO2中，中性Cu空位形成与相邻Cu原子空穴局域化的隙内态，而CuAlO2中Cu-on- al反位和CuGaO2中Cu-on- ga反位形成与自身空穴局域化的隙内态。在HSE06杂化泛函的框架下，Cu-on- al和Cu-on- ga的反位几乎满足广义Koopmans定理，但Cu-on- ga的空位不满足广义Koopmans定理。然而，无论fock交换参数控制的杂化泛函的凸/凹行为如何，Cu空位的受体能级的绝对位置几乎是恒定的，这表明价带最大值的确定主要与受体能级位置的准确预测有关。由Cu空位的自发形成决定的n型掺杂极限，即热力学平衡中费米能级的上限，相对于真空水平，几乎是所有CuMO2的能带排列所共有的。相反，导带最小值明显依赖于系统，这表明，随着cu空位形成的费米能级限制，载流子电子的强补偿只有在CuInO2中才能避免。这一发现表明，导带最小值的位置是先前提出的讨论和设计n型CuMO2掺杂的重要指标。
We investigate the native point defects in delafossite CuMO2 (M = Al, Ga, In) using first-principles calculations based on the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional approach. The Cu vacancies in all the systems show low formation energies and form relatively shallow acceptor levels, which would contribute mainly to the p-type conductivity. The hole compensation by the donor-type native defects does not essentially limit the p-type doping in all of CuMO2 under controlled growth conditions. In contrast, the acceptor-type native defects, especially the Cu vacancies, show low or even negative formation energies at high Fermi level positions in CuAlO2 and CuGaO2, thereby compensating carrier electrons to limit the n-type doping. The neutral Cu vacancy forms an in-gap state with hole localization to the neighboring Cu atoms in each of CuMO2, whereas the neutral Cu-on-Al antisite in CuAlO2 and the Cu-on-Ga antisite in CuGaO2 form in-gap states with hole localization to themselves. In the framework of the HSE06 hybrid functional, the generalized Koopmans' theorem is almost satisfied for the Cu-on-Al and Cu-on-Ga antisites, but not for the Cu vacancies in all of CuMO2. However, the absolute positions of the acceptor levels of the Cu vacancies are almost constant regardless of the convex/concave behavior of the hybrid functional controlled by the Fock-exchange parameter, suggesting that the determination of the valence band maximum is mostly relevant to accurate prediction of the acceptor level position. The n-type doping limits, namely the upper limits of the Fermi level in thermodynamic equilibrium, determined by the spontaneous formation of the Cu vacancies, are almost common to all of CuMO2 in the band alignment with respect to the vacuum level. In contrast, the conduction band minimum significantly depends on the system, which suggests, along with the Fermi level restriction by the Cu-vacancy formation, that strong compensation of carrier electrons is avoidable only in CuInO2. This finding indicates that the position of the conduction band minimum is an important indicator for discussing and designing n-type doping of CuMO2 as proposed previously.