Construction And Performance Of Two-dimensional Selenide Heterojunction Photodetectors

Two-dimensional（2D）van der Waals layered materials with atomic thickness offer new opportunities for the development of next-generation photoelectronic technique due to their unique properties such as good light absorption,high carrier mobility,wide tunable band gaps,and strong light-matter interactions.Due to the dangling bond-free surface of two-dimensional materials,the van der Waals heterojunction based on two-dimensional materials can combine the properties of multiple materials without the limitation of lattice matching,and pave the way for the integration at the atomic scale,which provides the direction for the development of high-performance,multifunctional photodetector.At present,there are relatively a few researches based on two-dimensional van der Waals heterojunction photodetectors,and the selection of materials is mainly based on two-dimensional materials,which limits the selection of materials to a certain extent.Moreover,there are still many defi ciencies in the design of devices,and the device performance needs to be further improved.In this dissertation,a series of high-performance photodetectors based on two-dimensional selenide heterojunction have been prepared by combining the properties of different materials and the energy band structure between materials,which broadens the selection range of heterojunction materials,improves the performance of self-powered photodetectors by using the energy band structure between materials,and improves the detection performance of two-dimensional material photodetector for weak light by using carrier recycling.In order to expand the selection range of materials for constructing heterojunction photodetector,p-type 1D Se nanotubes are prepared by physical vapor deposition,bulk InSe is obtained by Bridgman growth and the n-type InSe nanosheets are obtained by mechanical exfoliation,and then the 1D Se/2D InSe heterojunction is designed and constructed by combining the characteristics of two-dimensional material surface without dangling bonds.The transmission of photogenerated carriers at interface and phororesponse of 1D Se/2D InSe are studied in deatial.It is proved that the photodetector has good self-powered photoelectric detection performance.At zero bias voltage,the responsivity of the device can reach to 110 mA/W,and the response speed is 37 ms,which is about one order of magnitude faster than that of single InSe（600 ms）and Se photodetectors（350 ms）.The imaging capability of 1D Se/2D InSe heterojunction photodetector at zero bias is verified by applying the device as a single pixel point.In the research of regulating the performance of self-powered photodetector,InSe/WSe₂/SnS₂ heterojunction is constructed.Combined with theoretical simulation calculation,the regulation of light-induced electric field on the built-in electric field of InSe/WSe₂ heterojunction is systematically studied.It proves that the light-induced electric field can improved the photoelectric performance of the InSe/WSe₂heterojunction,and the responsivity of InSe/WSe₂ in InSe/WSe₂/SnS₂ heterojunction can reach to 550 mA/W which is about 50 times increase compared to single InSe/WSe₂ heterojunction at zero bias.The strong built-in electric field improves the response speed by an order of magnitude（InSe/WSe₂/SnS₂:110μs,120μs;InSe/WSe₂:3 ms,2.8 ms）and shows significant improvement in imaging quality for imaging applications.In order to improve the sensitivity of photodetector to weak light,InSe/GaSe heterojunction is constructed,and the built-in electric field is used to separate photogenerated carriers.InSe is designed as an electron transport channel and GaSe is used as a hole trapped layer,and the mechanism of carrier recycling to enhance the detectivity of InSe photodetector is systematically studied.It proves that the InSe photodetector base on InSe/GaSe heterojunction owns a high gain（10⁷）,the responsivity and detectivity can reach to 1037 A/W and 1×10¹⁴ Jones,which is 40times larger than that of single InSe photodetector,and it has lower detection limitation（InSe/GaSe,1μW/cm²;InSe,10μW/cm²）.In addition,the imaging applications also prove InSe photodetector based on InSe/GaSe heterojunction has stronger detection ability for weak light.