Research Of Two-Dimensional Te-based Van Der Waals Heterojunction Short-wave Infrared Photodetectors

The short-wave infrared（SWIR,λ=1-3 μm）has been widely used in various fields of the military and civilian economy,including Machine vision,security monitoring,biological science,and other aspects.The current commercial SWIR photodetectors are typically based on Hg Cd Te,In Ga As,and In As/Ga Sb type-II superlattices.However,these materials generally have disadvantages of the complicated preparation process,high cost,and low substrate compatibility,limiting their further development and applications.The exploration of novel SWIR-absorbing materials and device design has become an important research direction in this field.Two-dimensional（2D）materials have the merits of the widely-tunable band gap,high carrier mobility,and danging bonds-free surfaces and have great application potential in room temperature SWIR photodetectors.At present,the widely studied2 D SWIR-absorbing materials mainly include semi-metallic graphene,Pt Se2 and Mo Te2,black phosphorus,and doped black phosphorus.Nevertheless,the gapless semi-metals increase the dark current,while black phosphorus suffers poor ambient stability.As a new type of narrow-bandgap semiconductor,the application of two-dimensional tellurium（Te）nanomaterials in SWIR photodetection has gradually attracted the attention of researchers.Compared with other existing materials,2D Te exhibits superior room-temperature carrier mobility and excellent environmental stability.In addition,its unique helical-chain crystal structure leads to strong in-plane anisotropy,which can be directly used for polarized infrared detection.This thesis starts from the preparation of large-scale 2D Te nanosheets and develops a new method for the controllable thinning of Te.On this basis,different types of van der Waals（vd W）heterojunction structures are designed to enhance light absorption and reduce device darkness current,so as to achieve high-performance SWIR photodetection.The main research findings are as follows:1.High-quality single-crystalline Te nanosheets with length >100 μm and width >30 μm were synthesized by hydrothermal method and systematically characterized.The spontaneous thinning of Te nanosheets in deionized water was observed,and ultrathin Te nanosheets with a thickness of 2.6 nm and low surface roughness were successfully fabricated.Based on this,a new method for controllable thickness thinning of Te nanosheets by the KMn O4 oxidation-etching process is proposed.A controllable transfer technique for hydrothermally synthesized 2D Te nanosheets was also developed.2.A Te/MoS₂ vd W heterojunction short-wave infrared photodetector was designed and constructed.The heterojunction exhibits excellent field-effect transistor characteristics with a current on/off ratio exceeding 107 and a subthreshold swing of150 m Vdec-1.The photodetector spectral response range covers the entire short-wave infrared band,and the peak responsivity reaches 86 AW-1,24 AW-1,and 2 AW-1 under the illumination of 980 nm,1.55 μm,and 3.0 μm,respectively.3.A mixed-dimensional vd W photodiode was constructed based on 2D Te and1 D CdS nanoribbons.The heterojunction exhibits excellent self-driven photoresponse properties,enabling broad spectral detection from visible light to short-wave infrared（1.55 μm）range.Under 520 nm illumination,the device exhibits a high responsivity of 98 m A/W and external quantum efficiency of 23%.At the same time,due to the suppression of dark current,the current switching ratio of the device reaches 9.2×103,and the specific detection rate reaches 1.9×1011 Jones.