| Due to the absorption of the ozone layer,the 200 nm-280 nm ultraviolet band signal in the atmosphere is significantly reduced by the influence of sunlight.Therefore,solar-blind ultraviolet photodetectors that detect signals in this band have great advantages.It has great application potential in the fields of missile tracking,fire warning,ultraviolet communication,and biomedicine.The band gap of gallium oxide is 4.2-53 eV.It is a wide band gap semiconductor material with a direct band gap.As a representative material in the third generation of semiconductors,it has excellent chemical and thermal stability.In addition,it has a wide range of application prospects in semiconductor devices.?-Ga2O3 with a band gap of 4.9 eV is an ideal material.Its corresponding absorption wavelength is 253 nm,which is located in the solar-blind spectral region.At the same time,it has a flexible and adjustable band gap compared with alloy materials,which make it an ideal solar-blind photoelectric detection material.The quality of the ?-Ga2O3 film is directly related to the performance of the photodetector.At present,researchers usually use methods such as doping and heterojunction to improve device performance,but there are few means to improve the film quality directly.In this paper,using the interface effect between the substrate and the film,the ?-Ga2O3 epitaxial film was prepared on miscut substrate by metal organic chemical vapor deposition(MOCVD)and magnetron sputtering.The ?-Ga2O3 film was tested and analyzed by X ray diffraction(XRD),scanning electron microscope(SEM)and other characterization equipments.At the same time,it is difficult to obtain large area epitaxial films,because the three-dimensional materials are grown on three-dimensional(3D)substrate materials with strong covalent bonds.Although large-scale films can be obtained by laser sputtering and chemical methods,the cost is high and it is difficult to find a suitable sacrificial layer.Therefore,we transfer graphene as an intercalation layer to the substrate,and use graphene(GR)van der Waals force to preparation of epitaxial thin films on it.This will lay an experimental foundation for the subsequent preparation and transfer of large-area thin films.The experimental results are as follows:1.We prepared(201)?-Ga2O3 thin films on the(0001)sapphire single crystal substrates with miscut angles of 0°,4°,6°and 8°through the MOCVD,respectively.XRD and SEM test results show that the ?-Ga2O3 film growing on a 6° miscut sapphire substrate has the best crystallinity.The main reason is that the ?-Ga2O3 film preferentially nucleates at the steps,spreads and grows along the surface of the steps,which reduces the dislocation density and the number of grain boundaries,improving the crystal quality;2.A solar-blind ultraviolet photodetector was prepared on the obtained film,using the photolithography technology.And a photoelectric test platform including a semiconductor tester was used to test the photoelectric characteristics of the detector.We found that the photoelectric characteristics of epitaxy ?-Ga2O3 changed by selecting substrates with different bevel angles.In particular,Under the condition that the parameter of light is 5 ?W/cm2 and 254 nm at 5 V,the responsivity and detection of the ?-Ga2O3 film growing on a sapphire substrate with a 6° bevel angle reached 1.36 A/W and 5.6×1014 Jones respectively.It is much higher than solar-blind photodetectors on other miscut substrates;3.We transfered a single layer of graphene on a(0001)sapphire substrate,and prepard a ?-Ga2O3 film on the substrate contains graphene intercalation by magnetron sputtering.The optimal growth conditions for ?-Ga2O3 films deposited on a substrate with a single-layer graphene intercalation were obtained by control experiments.The best growth temperature was 650?,and the pressure was 2.8 Pa.According two-part experiments,this article explores the regulation mechanism of the miscut substrate on the epitaxial film,and a conclusion is drawn that the epitaxial film on the 6° miscut substrate has the highest crystalline quality and photoelectric performance.Moreover,it explores the optimal growth conditions for the deposited films on the substrate with graphene intercalation,which lays the foundation for subsequent work. |
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