不同价态Mn掺杂InN电子结构、磁学和光学性质的第一性原理研究

采用密度泛函理论体系下的广义梯度近似GGA+U平面波超软赝势方法,在构建了纤锌矿结构的InN超胞及三种不同有序占位Mn~(2+),Mn~(3+)价态分别掺杂InN超胞模型,并进行几何优化的基础上,计算了掺杂前后体系的电子结构、能量以及光学性质.计算结果表明:Mn掺杂后体系总能量和形成能降低,稳定性增加,并在费米能级附近引入自旋极化杂质带,体系具有明显的自旋极化现象.掺杂不同价态的Mn元素对体系电子结构和磁学性质产生了不同的影响.电子结构和磁性分析表明掺杂体系的磁性来源于p-d交换机制和双交换机制的共同作用,Mn~(3+)价态掺杂有利于掺杂体系的居里温度达到室温以上.与未掺杂InN相比,不同价态Mn元素掺杂后体系的静态介电函数显著增大,掺杂体系介电函数虚部和吸收光谱在低能区域出现了较强的新峰,分析认为这些新峰主要来自与费米能级附近自旋极化杂质带相关的跃迁.

First-principle study on electronic structures,magnetic, and optical properties of different valence Mn ions doped InN

InN,as an important Ⅲ-nitride,has high electron mobility and low electron effective mass,so it has a wide range of applications in optoelectronic devices,high-frequency high-speed devices,and high-power microwave devices.The Ⅲ-nitrides based dilute magnetic semiconductors (DMSs) can be developed by leveraging the existing fabrication technology for Ⅲ-nitride semiconductor electronic devices,leading to novel semiconductor spintronic devices with a multiplicity of electrical,optical,and magnetic properties.It has been reported that room temperature ferromagnetism exists in InN nanostructures and thin films as well as InN-based DMSs systems.However,the origin mechanism and the formation mechanism of ferromagnetism in these materials have not been fully understood.In Ⅲ-V compound semiconductors,the transition element Mn ions exist mostly in the form of Mn²⁺ valences while it is also possible for them to emerge in Mn³⁺ valence states under certain conditions.Although Mn²⁺ and Mn³⁺ valance states affect the physical properties of the doped semiconductor differently,there lacks in-depth understanding of such different effects resulting from Mn doping in InN. Under the framework of the density functional theory,in this paper we adopt the generalized gradient approximation (GGA+U) plane wave pseudopotential method to calculate the electronic structure,energy and optical properties of undoped InN and InN doped with three different orderly placeholders of Mn²⁺ or Mn³⁺ after geometry optimization.The conducted analysis shows that the system exhibits lower total and formation energies,and improved stability after Mn doping.Manganese doping introduces a spin-polarized impurity band near the Fermi level,and as a result the doped material system has obvious spin polarization.Doping with different valences of Mn ions lead to varying effects on the electronic structure and magnetic property of the material system.The analyses of electronic structure and magnetic property show that both the p-d exchange mechanism and the double exchange mechanism play important roles in the magnetic exchange of the doped system,and Mn³⁺ doping helps to push the Curie temperature above the room temperature.Comparing with the pure InN,the value of the static dielectric function of the doped system increases significantly.The present analysis concludes that the imaginary part of the dielectric function and the absorption spectrum of the doped system presents strong new peaks in the low-energy region due to the electronic transition associated with the spin-polarized impurity band near the Fermi level. Broadly,this work sheds new light on the microscopic mechanism for the magnetic ordering of Ⅲ-nitride based DMSs,and lays a foundation for developing the novel Ⅲ-nitride based DMSs and devices.