Research On Fabrication Of Novel Photodetectors Based On Two Dimensional Semiconductor Materials And Their Property

Due to the limitations of lithography and transistor structure,the integrated circuit industry is approaching the bottleneck in the post-Moore era.As one of the effective solutions to break through the stalled integration of traditional silicon-based chips,two-dimensional materials became an important theme of the International Electron Devices Meeting(IEDM)in 2021,showing the long-term thinking of the current academic and industrial circles on two-dimensional materials for advanced optoelectronic devices.At the same time,two-dimensional materials are also an excellent platform to study the spin,energy valley and other multi-dimensional degrees of freedom.In this thesis,from the perspective of optoelectronics,we focus on the the transmission and photocurrent regulation of photocarriers generated by photoexcitation in two-dimensional material devices,and study the signal transmission and regulation of photodetectors and valleytronics devices at room temperature.In the two-dimensional transition metal dichalcogenide(TMDs),the bandgap of semiconductor increases with the decrease of the material thickness,and the indirect band gap changes to direct band gap in monolayer,which makes the contrasting+K and-K valley in the momentum space of TMDs hexagonal structure in the position of direct bandgap,which can promote the realization of the excitation and detection of energy valley.Moreover,there are abundant crystal phases in TMDs,such as 3R phase,whose unique stacking mode breaks the structrue inversion symmetry(also known as spatial symmetry),providing an efficient research platform for the modulation of spin-valley polarization current.In the field of infrared detection,compared with bulk semiconductors,two-dimensional meterials have the advantages of simple manufacturing process,high surface quality,flexible heterogeneous stacking way,and easy integration into silicon based devices.However,due to the atomically thin thickness of two-dimensional materials,their light response is usually lower due to their weak light absorption,prompting researchers to propose various strategies to enhance the absorption efficiency of devices.The main research contents of this thesis are as follows:1.The influences of the preparation conditions,such as metal electrode deposition mode and metal semiconductor contact mode,on the electrical and optical properties of the device were studied,and the influences of the preparation and testing environment on the stability of atomically thin two-dimensional materials were determined,which provided a reference for photocurrent testing.2.Based on the 2H phase TMDs molybdenum disulfide(MoS₂),a field effect transistor(FET)with silica(SiO₂)as gate dielectric was prepared.It was determined that there was no circular photogalvanic effect(CPGE)in the multi-layer 2H phase MoS₂device with structure reversal symmetry.Van der Waals(vdW)contact and strongly bonded 3R MoS₂ devices have been fabricated,and obvious and stable CPGE effect has been observed in A-exciton resonance test under 633 nm illumination,with dichromatic ratio of 45%.The latter structure shows good stability under different source-drain bias voltages.Linear polarization term,circular polarization term and polarization independent term are extracted from the fitting curve,and good linear dependence on source-drain voltage is obtained.3.Based on narrow band gap two-dimensional semiconductor material tantalum nickel selenide(Ta₂NiSe₅),the photoelectric properties of visible light to mid-infrared photoelectric detection at room temperature are studied,and good photoelectric response to visible light and near infrared is shown.On this basis,the heterostructure was designed to improve the light absorption efficiency and photocarrier separation efficiency of the device,and the vertical heterostructure of MoS₂/Ta₂NiSe₅ was prepared by dry transfer.A photodetector with low dark current and fast response is realized.