Point Defects In Two-dtmenstonal Structures Of ?-group Nitrides

The two-dimensional nanomaterials of ?-group nitrides show a huge advantages in areas such as communications,energy,semiconductor devices and optoelectronic because of theirs unique electronic structure,good stability and excellent photoelectric properties.Among a large number of nitride materials,aluminum nitride(AIN),gallium nitride(GaN)and indium nitride(InN)are of great concern.Their wide band gap,excellent electronic and optical properties make them favored in the application of optoelectronic devices.The introduction of defects cannot be avoided in the process of material growth and preparation when using mechanical and liquid stripping methods or chemical vapor deposition.Due to the low-dimensional structural characteristics of monolayers,the defects contained in them will have a more significant impact on the properties than in bulk materials,which makes the properties of materials very different from those of perfect materials.However,the influence of defects on monolayers is not always negative,and it is also an important method to regulate their physical properties.Therefore,systematic and comprehensive defect research is of great significance to understand two-dimensional materials better.The specific research contents of this paper are as follows:First principles was used to study the point defects in the two-dimensional structures of ?-group nitrides.In the Hexagonal nitrides monolayers with defects,all structures are chemically stable,and the cohesive energy values has no obvious change compared with the perfect structures.The vacancy of N-atom shows metallic and no magnetism.The vacancy and replacement of metal atoms show obvious effect on the electronic properties.They bring unpaired electrons to the system,which makes the structures appear magnetic moment.In the cases of metal atoms absence,the system are transformed from the indirect band-gap semiconductors into the half-metal materials,while in the cases of metal atoms replacement,the systems are still semiconductors.As a supplement,the geometric and electronic properties of AlGaN and InGaN in Hexagonal structures are also studied.All the structure are chemically stable,and there is a good linear relationship between the lattice constant and cohesive energy and the doping concentration while slight bowing effect is observed for the band gap.The doping structures extend the group-III nitride materials,and provides the possibility to make better optoeletronic devices.Another focus of this paper is Haeckelite structure nitride.We chose the GaN monolayer as a representative to research the point defects in Haeckelite structure nitrides to improve the efficiency.Calculation results show that the regulations of Ga or N atoms'lack and replace are similar to which in the Hexagonal nitrides.However,the absence and exchange of two-atoms need to be analyzed separately.Both structures of Ga-N atoms lack are transformed from semiconductor to half-metal,while the degree are slightly different.A kind of Ga-N atoms exchange structure is similar to the perfect structure,while another occurs lattice reforming and tiny magnetic moment.These defect calculations can help us better understand the nitride structure of Hexagonal and Haeckelite.The transformation of electronic properties has a very broad application prospect in practice.