Theoretical Simulation And Experimental Study On The Photoelectric Properties Of Graphene-PbS Quantum Dot Vertical Heterojunction Structure

Photodetectors are widely used in many fields such as automatic driving,satellite remote sensing,atmospheric monitoring,security surveillance,agricultural cultivation,and so on.The traditional silicon photodetector has been maturely developed and applied in the field of photoelectric detection and imaging.However,the development of silicon-based semiconductor devices has been close to the limit of Moore’s law,and also facing the bottleneck of device size reduction to the nanometer range,so exploring new semiconductors to solve the problem of Moore’s law limit is one of the methods worth exploring.Two-dimensional materials have ultrathin channels with atomic layer thickness,no hanging parts on the surface,can be built with a high degree of freedom heterojunction,and various control methods.These characteristics make two-dimensional materials have broad application prospects in the field of new optoelectronic devices.As a typical representative of two-dimensional materials,graphene has ultra-high carrier mobility,broad spectral response,and extremely short carrier relaxation time.These properties make graphene have great potential for broad-spectrum,ultrafast photodetection.However,the short absorption path,low optical absorption rate,and short lifetime of photogenerated carriers of a single graphene photodetector severely limit the application of graphene in the field of photodetection.This paper takes the solution of these problems as the entry point,and will mainly focus on the combination of graphene and zero-dimensional quantum dots.Firstly,the mechanism of its photoelectric response is theoretically simulated,and then a graphene/Pb S/graphene vertical heterojunction photodetector is designed and fabricated,and its photoelectric properties are tested.The main contents are as follows:.（1）First,The Kretschmann-Raether prism coupling model was established by using the finite element simulation software COMSOL,The surface plasmon resonance of the graphene-Pb S quantum dot coupling model was simulated and calculated,and the optical simulation of graphene was derived and calculated using MATLAB.The plasmon resonance intensity in different situations was analyzed,and it was found that with the increase of the particle diameter of the quantum dot,the surface plasmon resonance electric field intensity gradually increased.With the increase of the incident light wavelength,the electric field intensity of the surface plasmon resonance first increases and then decreases,and the most obvious surface plasmon resonance is obtained at the wavelength of 1260 nm,and the optoelectronic performance of the device is optimal.（2）the patterned metal electrode was prepared on Si/SiO₂ substrate by ultraviolet lithography and electron beam evaporation process,and then the graphene material was transferred by the PMMA（poly-methyl methacrylate）-assisted transfer method,and finally the graphene/Pb S quantum dot/graphene vertical heterojunction photodetector was prepared by using spin coating process of quantum dots.（3）The photodetective capabilities of the devices with different structures is stematically characterized by an integrated photocurrent test system built in the laboratory.The results show that the devices with vertical channels have higher photocurrent response,the introduction of Pb S quantum dots significantly improves the optical absorption of the graphene photodetector,the fast separation of photogenerated carriers occurs at the interface between graphene and quantum dots,and the rise and fall times of the devices are 0.83 ms and1.71 ms,respectively,under the illumination of a light source with 2 V bias voltage at 1300nm wavelength.And the device has a responsivity of 14.31A/W and a specific detection rate of 6.61×10¹⁰Jones under the excitation of light with a wavelength of 1300nm and an optical power of 1.81 u W/cm².