Graphene/GaN Interface Electronic Properties:A First Principle Study

Research and application of GaN and graphene are hotspots all over the world.On one hand,it is because GaN is the third generation semiconductor materials in making microelectronic and optoelectronic device.On the other hand it is because graphene is a"super" material with high strength,high conductivity and high transmission.The combination of graphene and semiconductor will bring graphene a much broader application prospect.And the research of graphene/GaN composite system is of importance.With the first-principles method,the graphene/GaN heterojunction are investigated.Comparison of the graphene(2 × 2)/GaN((?)×(?))and graphene(3(?)× 3(?))/GaN two kinds of structure.The band structure,the density of states,the work function,and charge density difference are calculated systematically.It is found that both of graphene(2 × 2)/GaN((?)×(?))and graphene(3(?)× 3(?))/GaN(4 × 4)are mediated mainly by van der Waals force interaction.Valence band top and conduction band bottom of system appear at Γ points.The graphene(2 × 2)/GaN((?)×(?))is a direct gap semiconductor,the band gaps and the work function are obtained to be 0.12eV and 5.26eV,respectively.The graphene dirac points disappear at K points.Besides,the effective mass at the bottom of the conduction band and the top of the valence band at the Γ point are 0.27m0 and 0.29m0,respectively,and m0 is the quality of free electrons.While the graphene(3(?)× 3(?))/GaN(4 × 4)heterojunction band gaps and the work function are obtained to be 0.01eV and 3.26eV.Beside we study the band gap varies with the applied electric field.It found that the band gap reached the maximum 0.016eV when electric field is 0.75V/A.Graphene(3(?)× 3(?))/GaN(4×4)heterojunction easier to use as transparent electrode materials,and improve the conductivity and luminous efficiency of traditional photoelectric devices.The results offer theoretical data for the design and application of graphene/GaN heterostructure.