Theoretical Exploration Of TM-F/C-O Co-Doping To Improve The P-Type Conductivity Of AlN

During the past decades,aluminum nitride（AlN）,as a widest and direct band gap（6.2e V）semiconductor among group-Ⅲ nitrides,has great application prospect in developing the ultraviolet light sources（light emitting diode and laser diodes）.The device performance of AlN in practical applications depends largely on its conductivity.In previous studies,it was found that AlN could obtain effective n-type conductivity by doping donor type dopants.However,it does not exhibit effective p-type dopability,which limits its possibility in practical application.Therefore,finding a suitable acceptor dopant to make AlN have efficient p-type conductivity is one of the urgent problems to improve its practical application value.In addition,first-principles calculations have evolved from simple explaining and supporting experiments to powerful tools for predicting new materials and their properties.In this paper,based on first-principles calculation,appropriate dopants were selected to improve the p-type conductivity of AlN,and the doping methods to further improve the p-type conductivity of AlN were discussed,which provided a theoretical basis for the experimental design and research of high-performance AlN.The main research contents of this paper are as follows:1.Explore theoretically transition metal impurity to make AlN obtain efficient p-type conductivity.We propose that Zn and F co-doping is an effective strategy to achieve excellent p-type AlN through first-principles calculations.Nine transition metal（TM）elements from group 10 to 12 are selected to explore the potential dopants.Zn_Alshows the lowest defect formation energy and transition level among the considered TMs.Interestingly,there is a closely relation between the strength of p-d hybridization and defect formation energy in the considered TM dopants.On the other hand,Zn and F co-doping(F_N-3Zn_Al)further decreases the defect formation energy and transition level,remarkably enhancing the solubility of Zn acceptor and carrier concentration（i.e.excellent p-type conductivity）.These results are rationalized through the analysis of the projected density of states of doped systems.2.Explore theoretically of co-doped carbon（C）impurity and oxygen（O）impurity to improve p-type conductivity.As previously reported,O_Nand C_N as inevitable defects can even reach to very high concentrations that will affect the electrical and optical properties.Meanwhile,co-doping as an effective method has been widely used in defect design to decrease formation energy and transition level.The satisfactory band gap and high concentration of impurity drives us to revisit the oxygen（O）and carbon（C）impurities in AlN.In this report,we calculated the formation energy and transition level of isolate O_N,2O_N-C_N complex,C_N and 2C_N-O_N complex doped AlN based on the first principle calculation which indicates that the formation energy and transition level are both reduced for the co-doping compared with mono-doping.And we discussion the defect physics of the reduction in detail.