First-principles Calculations Of Adsorption Properties Of Two-dimensional GaN And Two-dimensional GaN-based Heterostructures

As the third-generation semiconductor,bulk GaN with a wide band gap,high thermal conductivity and good chemical stability shows a very broad application prospect in electronic,optoelectronic and power devices.With the emergence of graphene,two-dimensional materials have gradually entered people’s vision recent years.In 2006,researchers successfully predicted the existence of two-dimensional GaN by first-principles calculation,and it was successfully prepared by the method of graphene encapsulation for the first time in 2016.The two-dimensional GaN have higher band gap and better quantum effect than bulk GaN,thus the semiconductor devices produced by two-dimensional GaN can withstand higher voltage.But the present experimental conditions can’t overcome the lattice mismatch in the process of two-dimensional GaN growth,and the preparation of two-dimensional GaN is buckling,thus seriously affect its physical and chemical properties and in the actual application,by which the first principles calculations in exploring the properties of two-dimensional GaN is still an indispensable tool.It is known that adsorption plays essential role in investigating how to regulate the physical and chemical properties of two-dimensional GaN,and there are many studies on the adsorption characteristics of two-dimensional GaN recent years.For example,the adsorption of B,C and N atoms on the surface of two-dimensional GaN can not only regulate the band gap of two-dimensional GaN,but also induce the spin polarization behavior of electrons in two-dimensional GaN.However,the studies on the adsorption characteristics of two-dimensional GaN are not systematic so far.It is still unknown when the adatoms in the same period or the same main group,the twodimensional GaN have the same adsorption characteristics and change rules.In addition,the research so far only stays on the two-dimensional GaN monolayer,but the adsorption properties of the heterostructures constructed by two-dimensional GaN and other two-dimensional materials are still unknown.Thus,we explored two-dimensional GaN absorbed with atoms of IIIA-VIIA groups in the range of 2nd to 4th periods and two-dimensional GaN/AlN heterostructure absorbed with B,C,N,O and F atoms through the method of the first-principles calculations,and the conclusions are shown below:In two-dimensional GaN adsorbed with group IIIA-VIIA group in the range of 2nd to 4th period adsorption systems,the chemisorption occurs for all selected adatoms and the adsorption energy of C is the highest because of its special adsorption configuration.The electronic structure studies indicate that the adatoms introduce magnetic feature with spin-polarized properties except for the group VIA atoms.Moreover,a semiconducting state presents in the groups IIIA,IVA and VIA atoms adsorbed 2D GaN,while a half-metallic state appears in 2D GaN after the adsorption of VA and VIIA atoms,which makes the latter higher work functions.Such regular modifications in physical properties of 2D GaN induced by adsorption could potentially allow use of this material in diverse electronic,optoelectronic,and spintronic applications.The adsorption of B,C,N,O and F atoms by two-dimensional GaN/AlN heterostructure is still chemisorption.In all the adsorption systems with the same heterostructure,N atom has the lowest adsorption energy.Except for the adsorption system of O atom,all the adsorption systems exhibit the spin polarization behavior,which results in the magnetic in the adsorption systems.In addition,all the adsorption systems maintain the semiconductor properties of the heterojunction without the transformation of semi-metallic properties,which is different from the results of the intrinsic 2D GaN adsorption system.