Growth Of VO₂ Film And Interfacial Characteristics Of N-VO₂/p-GaN Base Heterojunction

Vanadium oxide are equipped with the characteristics of insulator to metal transformation in the critical temperature?Tc?and accompanied by the break behavior of resistance and near-infrared transmittance.The T_c of VO₂ is 68^oC which is closest to the room temperature.Below the Tc,VO2 film shows the insulator phase with high resistivity;above the T_c,VO₂ film is metal phase.The transformation of crystalline structure that is from monoclinic structure insulator phase with low temperature to retragonal rutile structure metal phase with high temperature in the processes of phase transformation,and the phase transformation of VO2 film is reversible because of the reversible crystalline structure.Due to the peculiar transformation characteristic,VO₂ film has infinite application prospects in the optical and electrical switch,laser protection and smart window and so on.While the complexity of vanadium oxide and the T_c of VO₂ film limits the application of VO₂ as advanced material.the T_c of VO₂ film can be reduced to room temperature by doping,but the range of phase transformation weakens obviously and the thermal hysteresis loop of transformation becomes wide.Thus,growing VO₂ film with single phase which can be controlled the T_c of phase transformation precisely and maintaining the break of optical and electrical characteristics are important particularly.The paper is aimed at getting the VO₂/p-GaN heterojunction and the high quality VO₂film with different thicknesses which growth on p-GaN substrate by oxide-molecular beam epitaxy?O-MBE?.Though changing the thickness of VO₂ film to lead in the stress to control the transformation characteristics of VO₂ film and explore the optical and electrical characteristics of VO₂ film and VO₂/p-GaN heterojunction respectively.The content of this paper:?1?Growth the high quality VO₂ film with various thicknesses on the commercial p-GaN/sapphire substrate by O-MBE,and though changing the thickness of VO₂ film to lead in the stress to control the transformation characteristics.X-ray diffraction?XRD?,scanning electron microscope?SEM?and atomic force microscope?AFM?are used to analyze the crystalline structure and morphology.?2?Studying the resistance transformation characteristic of VO₂ film with various thicknesses on the commercial p-GaN/sapphire substrate in the various temperature.Studying the electrical stability of VO₂ film in the relative exposure environment for one year and the change of various temperature control the transformation behavior of VO₂/p-GaN heterojunction form pn junction to schottky junction.?3?Researching the optical transmittance of VO₂ film grown on p-GaN/sapphire substrate,including the optical transmittance change of VO₂ film with various temperature in the range of near-infrared and intermediate infrared and the optical transmittance of VO₂ film with various temperature in the specific wavelength of near-infrared.And the resistance changes of VO₂ film with various temperature in the effect of solar simulator or not.Through the experiments and characterization,we obtain the high quality VO₂ film with single phase and uniform grown on p-GaN/sapphire substrate,and observe the reversible insulator-metal transformation?MIT?at 56.9 ^oC and 62.9^oC that lower than the T_c?68 ^oC?of VO₂ single film.The elevatory temperature change the heterojunction form pn junction to schottky junction.The VO₂ film is still equipped with reversible transformation a year later,but the mutability become bad.The optical transmittance changes of VO₂ film in the effect of near-infrared at 2?m shows the change of 28%.The resistance of VO₂ film in the solar environment becomes lower than there is no solar,but is still equipped with the resistance transformation.