Study On Fabrication And Resonse Mechanism Of Terahertz Photodetectors Based On Type-? Dirac Semimetal

Recent years have witnessed rapid progresses made in the photoelectric performance of two-dimensional materials represented by graphene,black phosphorus and transition metal dichalcogenides(TMDCs).Despite significant efforts,photodetection technique capable base on two-dimensional materials for longer wavelength,higher working temperature as well as fast responsivity is still facing huge challenge due to lack of best among bandgap,dark current as well as absorption ability.At the meantime,in recent years,with the rapid development of semiconductor technology and the rapid exploition of photodetector application field,higher requirements are put forward for photodetectors with excellent performance,the detection of terahertz radiation in the transitional region between photonics and electronics has been of great concern particularily.The research of terahertz technology involves physics,chemistry,material science,semiconductor science and technology,vacuum electronics and other disciplines,which is a typical interdisciplinary frontier science and technology field.Exploring topological materials with nontrivial band transport leads to peculiar properties of quantized phenomena such as chiral anomaly,magnetic-optical effect,which enables novel feasibility for advanced optoelectronic device working at longer wavelength.The discovery of Dirac semimetal has hold great promise for manipulating the performance of photoelectric devices that related to nontrivial band topology.This paper mainly studies the application of new type-? Dirac semimetal materials in terahertz detection field,including the research of terahertz detector based on platinum telluride(PtTe₂)material,and the regulation of energy band structure of Ir_1-xPt_xTe₂material and the realization of high-performance terahertz detector.1.Platinum telluride(PtTe₂)is a new type-? Dirac semimetal material with a tiltedDirac cone energy band structure.The Dirac cone with a serious tilt in a particular momentum direction provides a new approach to research the anisotropic transport properties.In this content,we mainly studied the room temperature terahertz detector based on the low-dimensional structure of PtTe₂ material,and realized the high performance self-powered detection of 0.12 THz through the design of bow-tie shap antenna coupled with terahertz radiation.Due to the anisotropic type-? Dirac band structure,device can directly generate photocurrent at zero bias voltage,its responsivity can reach at 1.6 A/W and is enhanced to 3.8 A/W with a bias voltage of 100 m V.Under the weak effects of van der Waals forces of two-dimensional heterostructure interface,the synergetic integration of PtTe₂ with graphene in a vd W heterostructure leads to integrated properties including fast charge transferring and strong THz absorption,which is corroborated as an effective strategy for enhanced THz detection performance.The results show that topological semimetals like PtTe₂ are ideal materials for high performance optical detection systems in terahertz bands,which are particularly attractive for nondestructive imaging,remote sensing and biomedical applications.2.In type-? Dirac semimetals PtSe₂ and Pd Te₂,their Fermi levels are far away from the Dirac point,and we propose a new method of doping Ir Te₂ with Ptmetal element to explore and optimize their band structure.Combined with the first principles of theoretical analysis and experimental verification of angular resolution photoelectron spectroscopy,we prove the Ir_1-xPt_xTe₂ with the Ptdoping become an ideal type-? Dirac semimetal materials.Due to the different number of electrons,the Ptdoping concentrations can regulate the Fermi level of Ir_1-xPt_xTe₂ material system,and when the Ptdoping concentration reaches 0.3,the Fermi level of Ir_1-xPt_xTe₂ just contact with the Dirac point,which overcomes the shortage that the Dirac point and Fermi level are far away from each other in PtSe₂ material.On account of the Fermi level contact with type-? Dirac point,the metal-Ir_1-xPt_xTe₂-metal detector under terahertz radiation filed in the simulation shows the strongest terahertz radiation absorption in the system when x?0.3.As a result,the terahertz detector based on Ir_0.7Pt_0.3Te₂ material shows strong photoconductivity at room temperature,and has a great improvement in performance.The photoresponsivity of the detector can reach 0.52 A/W at 0.12 THz and 0.45 A/W at0.3 THz at room temperature,and it also has a fast response speed.Benefit from the van der Waals heterostructure of Dirac semimental,terahertz detector shows superior suppressed thermal-agitation noise ability,through in-depth analysis of the heterostructure contact between the Ir_1-xPt_xTe₂and graphene,seebeck coefficient difference of each part of the heterostructure and the difference of terahertz radiation absorption capacity,the detector of Ir_0.7Pt_0.3Te₂ material and graphene heterostructure shows excellent performance and has the equivalent noise power of 24 p W·Hz^-0.5.In addition,the detector can operate without biased voltage,comparable to the most advanced detectors.In this thesis,two new type-? Dirac semimetallic materials have been studied around the application of new materials in terahertz detection field.We have got high performance room temperature terahertz photodetectors based on type-? Dirac semimetal materials,explored its resonse mechanism,realized the competitive response performance and the preliminary imaging applications,these results lay an important research foundation for the exploration and realization of new topological materials in terahertz detection at room temperature,and provide an effective way for the study and application of the nontrivial topological band structures of Dirac semimetallic materials.