Research On Plasmon-enhanced Near-infrared Group-? Photodetectors

Silicon-based optoelectronic devices play an important role in modern optoelectronics because of their wide application in military and civil fields.In recent years,with the rapid development of emerging markets such as unmanned driving and biological pattern recognition,infrared photodetectors in silicon-based optoelectronic devices have attracted much attention and have become a current research hotspot.However,since the band gap of Si material is 1.12 e V,its absorption cut-off wavelength does not exceed 1100 nm.Ge material of the same family as Si,because of its smaller band gap(0.66 e V)and compatibility with Si-CMOS technology,has become one of the most potential silicon-based near-infrared detection materials.Although Ge photodetectors have great appeal in the detection of nearinfrared optical communication bands,the relatively low absorption coefficient of wavelengths exceeding 1550 nm is an important obstacle to its large-scale commercial application.Among several solutions,using the surface plasmon resonance effect to improve the light response near a specific wavelength is one of the effective methods.Among them,the light absorption enhancement effect comes from two mechanisms: 1)The band-to-band transition absorption of the material is enhanced by the local enhancement of the plasmon resonance electromagnetic field;2)The hot electrons in the metal nanostructure contribute to the photocurrent through the internal photoemission effect.Thereby achieving enhanced light response.Based on the above two absorption mechanisms,a new type of Ge-based plasma photodetector based on Au-Ge grating structure is proposed.The Au-Ge grating structure can combine the advantages of the interband transition of Ge material and the internal photoemission of Au / Ge Schottky junction.The dependence of the structure parameters on the device performance is analyzed by using the finite difference time domain(FDTD)simulation,and the optical absorption structure of the detector is optimized.The simulation results of optical absorption spectrum,electric field and absorption distribution show that the surface plasmon at the Au/Ge interface generates a locally enhanced electromagnetic field,and at the same time enhances the inter-band transition and internal photoemission effect,thereby realizing high-efficiency photoelectricity Probe.Process realization and performance characterization of the optimized device have been carried out.The results show that the device has an efficient detection capability for incident light with a wavelength of 1550 nm,with a responsivity of 0.38 A/W and an external quantum efficiency of more than 30%.At the same time,in the three near-infrared communication bands(C,L and U bands),the responsiveness of the device has been significantly improved.On this basis,a grating nanowire detector with resonant cavity structure is proposed.The optical absorption is further enhanced by multiple oscillations in the resonant cavity through the bottom Au grating.The simulation model is established and the influence of structure parameters on the device performance is analyzed.After optimization,there is an obvious narrow-band absorption near 1550 nm,up to 74%.At the same time,it is found that the width of the grating has the most obvious effect on the formant position.Therefore,a grating nanowire array photodetector with variable linewidth and resonant cavity is designed.Through this structure,it is possible to "customize" the specific waveband and the response characteristics of the photodetector can be improved.In this thesis,1550 and 2000 nm bands with various application prospects are selected to optimize the design,so that the formant position is near these two specific bands,and the corresponding absorptivity reaches 64%and 23% respectively.Therefore,not only the detection wavelength range is expanded,but also the dual band detection in the communication band is realized.Finally,considering different application scenarios,the polarization insensitive dual band plasma photodetectors with disk and ring structure are designed respectively.Based on this structure,the dual band absorption of 1310 nm and 2000 nm is simulated and optimized,and the final dual band absorption is 77% and 41% respectively.At the same time,the dependence of the structure parameters on the absorption characteristics of the device is deeply discussed.By adjusting the structure parameters,the selection and enhancement of different wavelengths are realized,and the optical response of the silicon-based Ge detector in specific wavebands is significantly improved,which provides a solid theoretical basis and practical experience for high-performance silicon-based photoelectric detection and its integration.