Zn,Cd掺杂AlN电子结构的第一性原理计算

First-principles Calculation of AlN Electronic Structure by Doping with Zn and Cd

基于密度泛函理论(DFT)框架下的第一性原理的平面波超软赝势方法(USPP),对Zn,Cd掺杂AlN的32原子超原胞体系进行了几何结构优化,从理论上给出了掺杂和非掺杂体系的晶体结构参数。计算了掺杂AlN晶体的结合能、电子态密度、差分电荷密度,并对计算结果进行了细致的分析。计算结果表明,Cd、Zn都可以提供很多的空穴态,是良好的p型掺杂剂,但是相对于Cd,Zn原子在AlN晶体中的溶解度更大,并且可以提供更多的空穴,有利于形成更好的p型电导。

AlN is a new type of direct wide bandgap Ⅲ-Ⅴ nitride semiconductor material. Because the AlN possesses of many interesting physics characteristics, it has attracted huge attention on potential applications. In addition, AlN is a type of direct bandgap semiconductor material with a very wide direct bandgap of 6.2 eV, as solid-state light sources, which are in the process of profoundly changing the way that human generates light for general lighting applications. Solid-state light sources possess of two highly desirable features, which set them apart from most other light sources： （i） they have the potential to create light with essentially unit power efficiency and （ii） the properties of light can be controlled to a degree. In another actual application, AlN as a kind of high-efficiency ultraviolet solid-state light sources is greatly important material to develop short wavelength ultraviolet light-emitting diodes. Microelectronic fabrication technologies and the enviromental sciences both require light source with shorter emission wavelengths, such as the former to imporve resolution in photolithography and the latter for sensors that can instantaneously detect hazardous particles. Furthermore, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. In recent years, the great importance of semiconductor material has been realized in the fabrication of the shoter emission wavelength light-emitting diodes, resulting in research on AlN thin film. At present, researchers have completed Si doped AlN n-type conduction with very strong conductivity. Lately, Nepal et al.made use of Zn doping to obtain p-type AlN. However, the efficiency of doping is quite low, the p-type AIN possesses of lower quantum energy, and the acceptor compositions need to be detected further. In this paper, we studied the efficiency of Zn and Cd as p-type doping in wurtzite AlN crystals. In the present study we performed the geometrical structure of Zn and Cd doped 32 atoms supercell of AlN, which is optimized by adopting the ultra-soft pseudopotential method of total-energy plan wave based on the destiny functional theory （DFT）. Cell parameters of both undoped and doped cells were calculated theoretically. crystals. The result of our calculation revealed the fact that both Cd and Zn atoms can provide a good deal of the state holes, which means that both of them are well p-type doping, nevertheless, comparing with Cd, Zn has a better solubility in AIN crystals, because Zn in AlN crystals can provide more the state of hole, which is propitious to come into being better p-type conduction. We prove that Zn is a better p-type doping ion than Cd.