Preparation And Characterization Of Zn And Mg Doped Ga₂O₃ Thin Films

Gallium oxide?Ga₂O₃?,with a band gap of 4.9 eV,is a new kind of very promising wide band gap semiconductor.Among the variety structures of Ga₂O₃?known as ?,?,?,? and ??,the most stable structure is monoclinic ? phase.?-Ga₂O₃ has many excellent physical properties,such as large bandgap,high puncturing field intensity,high dielectric constant,high transmittance in visible light and UV regions,good thermal and chemical stability.It has important application prospects in the future electronic devices,such as: solar blind ultraviolet photodetector,field effect transistor,transparent conductive electrode,etc.Similar to the common oxide semiconductor,pure ?-Ga₂O₃ usually exhibits n-type conductivity,the p-type conductivity in ?-Ga₂O₃ is difficult to obtain due to the self compensation effect of defects such as oxygen vacancies.However,the application of the device is often based on PN junction.Theoretically,two valence elements doping ?-Ga₂O₃ can realize p-type conductivity.In this work,the pure and Zn,Mg doped ?-Ga₂O₃ thin films were grown by magnetron sputtering process.The microstructure,optical absorption and elemental composition of the films were analyzed by X ray diffraction,Ultraviolet-visible spectrophotometer and X ray photoelectron spectroscopy.In addition,The metal semiconductor metal?MSM?structure photodetectors based on both the pure and Zn-doped ?-Ga₂O₃ films are prepared.The effect of doping on the quality of Ga₂O₃ films and the performance of the solar blind ultraviolet detector were studied.The contents and conclusions of this paper are as follows:?1?In this paper,the basic growth parameters of ?-Ga₂O₃ films grown were studied by magnetron sputtering and discussed the effects of different grown temperature and deposition pressure on the crystalline phase of the films.it is concluded that the best growth parameters of ?-Ga₂O₃ film is that the substrate temperature 750 ? and the sputtering pressure 0.8 Pa.?2?The prepared ZnO chips were placed on pure gallium oxide target.Different concentrations of Ga₂O₃ films doped separately with Zn by magnetron sputtering deposition system.The structure,composition,optical properties and electricalproperties of doped Ga₂O₃ films were systematically studied.The doped Ga₂O₃ films are still monoclinic system,As the ion radius of Zn2+ is larger than that of Ga3+,the diffraction peak of the doped thin film is shifted to lower angles.With the increase of the doping content,the optical band gap of the thin film becomes smaller,which is due to the impurity level.The doped films did not respond under 365 nm UV excitation.The maximum light and dark current ratio of doped films reached 110 under the excitation of UV light at 254 nm.while the maximum light and dark current ratio of pure Ga₂O₃ film reached 30.In addition,compared to the pure ?-Ga₂O₃ film,doped ?-Ga₂O₃ films photodetectors exhibit a faster photoresponse speed,which is due to the reduction of oxygen vacancy concentration.Mg-doped Ga₂O₃ films with different concentrations were deposited by magnetron sputtering deposition system,the effect of Mg doping on the structure and properties of Ga₂O₃ thin films was studied.As the ion radius of Mg2+ is larger than that of Ga3+,the diffraction peak of the doped thin film is shifted to lower angles.the metal semiconductor metal?MSM?structure photodetectors based on Mg-doped ?-Ga₂O₃ films are prepared.compared to the pure ?-Ga₂O₃ film,doped ?-Ga₂O₃ films photodetectors exhibit a faster photoresponse speed and the device has good repeatability and high stability under different bias voltage.?3?We have annealed the doped films under different temperature.With the increase of annealing temperature,the energy of atomic absorption is higher and higher,which makes the grains have enough energy to rearrange when they are preferentially oriented.So the crystallinity of doped films is getting better and better.When the annealing temperature is 900 ?,the preferential growth of Mg-doped Ga₂O₃ films changed.In addition,with the change of annealing temperature,the optical band gap of the doped films changed.