Novel Photodetectors Based On Two-dimensional Layered Materials And Their Heterostructure

The discovery of graphene in 2004 triggered a wave of exploring two-dimensio na l materials.Different two-dimensional materials were discovered successively,and the types of two-dimensional materials became extremely rich.In recent years,the development of assembly technology in preparing two-dimensional material heterojunction has expanded the research system of two-dimensional materials,and provided a material basis for studying the characteristics of new heterojunctions.By taking advantage of the unique advantages of different two-dimensional materials,the heterojunction can provide advantages of each material and the performance of related devices can be improved.Photodetectors based on two-dimensional materials heterojunctions exhibit excel ent optoelectronic performance,show great potential in improving the response speed,working efficiency,and extending wavelengt h response range of photodetectors.Therefore,they have become the research hotspot in the field of micro-nano optoelectronic devices.In this thesis,the basic characteristics of two-dimensional materials such as indium selenide?InSe?,sulfur-doped indium selenide?S-doped InSe?,graphene and molybde num disilicide?MoTe2?were studied.They were assembled into highly efficient photodetectors,including graphene/S-doped InSe heterojunction photodetectors,and InSe/graphene/Mo Te₂heterojunction photodetectors.We first briefly introduced the material system involved in this thesis,explained the performance parameters of the photodetector,and illustrated the assembly technology of two-dimensional heterojunctions.We then introduced experimental facilites,including the instruments used to prepare and characterize the materials,as well as the optoelectronic measurement platform.In the third chapter,we studied the photoelectric properties of S-doped InSe photodetectors and graphene/S-doped InSe photodetectors.A high-performance graphene/S-doped InSe photodetector was obtained by combining the advantages of S-doped InSe and graphene.By comparing the graphene/undoped InSe photodetectors,it is found that the heterojunction device based on graphene/S-doped InSe exhibit more excel ent photoelectric properties,and its photoresponsivity is up to 8×10⁶ A/W.The specific detectivity is as high as 7×10¹² Jones,and the photodetector has a fast photoelectric response.We believe that element doping is an effective method to improve the performance of photodetectors,and can be widely applied to photodetectors of various systems of two-dimensional materials.In the fourth chapter,we designed a new type of photodetector based on InSe/graphene/MoTe2 heterojunction,which exhibits excel ent photoelectric performance and achieves ultra-fast photoelectric response,with a rise time of 460 ns,and a fall time of 485 ns.Compared with the InSe/MoTe₂ heterojunction without graphene,the optical response time of InSe/Graphene/MoTe₂ heterojunction is increased by 5 orders of magnitude,and the response time is shorter than most of the photodetectors based on two-dimensional materials reported so far.In addition,our devices extend the response wavelength range up to 1400 nm,while the InSe/MoTe₂ heterojunction has a photoresponse wavelength limit of¹100 nm.Our device display a photoresponsivity of 11 A/W under visible light of 690 nm,an EQE of 1980%,and a specific detectivity of 2.17×10¹22 Jones.It also exhibits excel ent optoelectronic performance in the near-infrared light of 1300 nm,with a photoresponsivity of 2.88 A/W,and an EQE of275%.Through the measurement and analysis of our heterojunction devices,we have provided a new path for the realization of heterojunction photodetectors with ultra-fast photoelectr ic response and excellent photoelectric performance.