| Due to the strong absorption of the solar-blind ultraviolet radiation area(200 nm?280 nm)by the ozone layer,solar-blind ultraviolet detection technology has the characteristics of anti-environmental interference and all-weather work,and has been widely used in environmental monitoring,power industry,ultraviolet communication and other fields.?-phase gallium oxide(?-Ga2O3)is a direct bandgap semiconductor with a band gap of about 4.9 eV,and has excellent thermal and chemical stability.It is an ideal solar blind photodetection material.Although ?-Ga2O3 thin film has shown excellent application prospects for solar blind detection,its device performance still needs to be further improved.In this thesis,different substrates are introduced to control the orientation and crystal quality of ?-Ga2O3 films,and the optimal growth temperature of high-quality films is studied.And the tailoring of photoresponse characteristics through lattice mismatch and film orientation were in-depthly studied.Our results may provide a strategy to develop further high performance solar-blind photodetectors..The main research results are as follows:(1),(100)?-Ga2O3 thin films were deposited on(100)MgO and(100)MgAl2O4 single crystals substrates by RF magnetron sputtering at different substrate temperatures,XRD results showed that the crystallinity of the film is the best at 750?,which is the optimal growth temperature.The growth temperature was then set to 750?,(100)single-oriented ?-Ga2O3 films were grown on(100)MgO and(100)MgAl2O4 substrates by RF magnetron sputtering,while ?-Ga2O3 films grown on(100)STO and(100)LSAT substrates contained other orientations.(2)(201)?-Ga2O3 thin films were deposited on(0001)Al2O3 single crystal substrate by metal organic chemical vapor deposition(MOCVD)at different substrate temperatures.XRD results showed that the crystallinity of the film is the best at 750?,which is the optimal growth temperature.Then,the growth temperature was set to 750?,(201)?-Ga2O3 thin films were deposited by MOCVD method on three kinds of c-plane sapphire substrates which were without surface off-cut,with 4° and 6° surface off-cut.The results of ?-2? scan,rocking curve and pole figure showed that the ?-Ga2O3 film grown on 6° surface off-cut sapphire substrate has the best crystallinity.This is due to the high density nucleation centers brought about by the atomic steps of the surface off-cut substrate.(3)we show that by selecting substrates[i.e.(100)MgO,(100)MgAl2O4 and(0001)?-Al2O3],epitaxial ?-Ga2O3 films with(100)-or(201)-oriented could be fabricated.Compared with(201)?-Ga2O3 film,(100)?-Ga2O3 film has a larger grain size and fewer in-plane domain structures,and exhibits better crystal quality.Au/Ti interdigital electrodes were then fabricated on ?-Ga2O3films with different orientations by photolithography.The test results of solar-blind ultraviolet detection performance showed that,the(100)-oriented ?-?-Ga2O3 film on MgO present an enhanced responsivity of 0.1 A·W-1,a detectivity of 4.3×1012 Jones,a EQE of 0.49 and a photo-to-dark current ratio over 2×104 under 254 nm light(300?W/cm2),which is approximately one order of magnitude higher than(201)?-Ga2O3 thin film on sapphire. |
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