High Performance Narrow Band Near-infrared Photodetectors Based On 1T-WS₂/Si Heterojunction

Near-infrared?NIR?photodetectors show a great potential application in biomedical fields such as clinical diagnostics and therapeutic equipment.The novel two-dimensional transition metal chalcogenides?2D TMDs?have attracted much attention in near-infrared photodetectors because of their unique interfacial and optoelectronic properties.Among them,silicon-compatible TMDs/Si 2D-3D heterojunction photodetectors have great potential application value due to excellent photoelectric characteristics such as high speed and high detectivity.In this dissertation,high-performance TMDs/Si 2D-3D heterojunction has been constructed toward the fabrication of near-infrared photodetectors.The metal phase tungsten sulfide?1T-WS₂?was chosen to construct this heterojunction by using pulsed laser deposition?PLD?method.The synthesis of the high-quality 1T-WS₂ and optimization of the heterojunction narrow-band NIR response was systematically studied.Furthermore,the narrow-band NIR photodetectors will be used in pulse signal monitoring.The main research contents and results of this article are as follows:?1?For the first time,PLD method was used to synthesize two-dimensional WS₂ thin film with large area by controlling the deposition temperature,pulse laser energy density and other process parameters.Characterization of materials such as XPS indicates that the as-synthesized material is 1T-WS₂with high crystal quality and high conductivity.?2?The 1T-WS₂ films were deposited on Si substrate by PLD technique,and then in situ firstly constructed 1T-WS₂/Si vertical heterojunction.The photoelectric characteristics of the optimized device revealed that the heterojunction has poor visible light response and excellent narrow-band near-infrared light response characteristics of800-1500 nm,and the response range of silicon-based photodetectors in near infrared light is also widened.Additionally,the responsivity to 1550 nm infrared light is comparable to commercial In Ga As photodetectors,and The responsivity to 1064 nm is up to 0.8 A/W at zero bias,the response speed reach to 6.13?s.?3?Based on the principle of PPG pulse signal monitoring,a pulse signal measurement system,consisting of 1T-WS₂/Si heterojunction narrow-band near-infrared photodetector,980 nm light-emitting diode and amplifier,was constructed.The heart-rate values measured from this system are comparable to that of commercial PPG system.Especially,this device exhibited a good resistance to ambient light interference.These results suggest that the construction method of heterojunction is expect to boost the design and development of the 2D TMDs/Si heterojunction-based narrow band NIR photodetectors,and the 1T-WS₂/Si heterojunction-based narrow band NIR photodetectors shows potential application in PPG pulse monitoring.It provides a new route for the application of new nano-photodetectors in pulse signal monitoring.