Design Of CMOS-compatible Photodetector With Graphene Embedded In Silicon Nitride Ridge Waveguide

Waveguide-type photodetector is one of the core devices of the on-chip optical interconnection system.Its detection speed determines the upper limit of the response speed of the whole system.Graphene is a kind of material with the highest carrier mobility and fantastic photoelectric properties as far as we know.However,there exist some compatibility problems between waveguide-type photodetector based on graphene and CMOS process technology,which have become the biggest obstacles to realize the miniaturization and integration of such devices.The comprehensive comparison of the structure and processes of waveguide-type photodetector based on graphene is analysised,and a singlelayer graphene embedded in silicon nitride ridge waveguide photodetector(SLG-E-Si N-RW PD)is proposed in this paper.For the device structure,an interdigital metal doping electrode based on the surface doping effect is designed,and the effect of the waveguide structure parameters change on the light field distribution in the waveguide is simulated,then a ridge waveguide structureis designed and simulationoptimized in this paper.For manufacturing processes,a device manufacturing process flow based on CMOS process is designed,and some single-step processes are experimentally researched such as photolithography,lift-off,metal wet etching,graphene transferred by PMMA and deposite silicon nitride on graphene by PECVD.For the test process,a graphene quality test method in which optical microanalysis rough detection and Raman spectroscopy analysis fine detection are combined is designed in this paper.A mathematical model for optical microanalysis based on Fresnel's law is established.A simulation and optimization of the cladding thickness required for optical microscopy is worked out in which the strcture of waveguide core in this paper is set as an example.The simulation and design for waveguide is based on Lumerical MODE,the results show that,the electrical field intensities from 0 to 10 nm in the bottom core are totally as more than twice as the intensity on the ridge surface,when the silicon nitride waveguide has paremeters such as 400 nm for ridge height,1.3 ?m for ridge width and 320 nm for bottom core height.Appropriate process parameters for the single-step processes are developed,and the compatibility to CMOS process technology is verified by the experimentally study.The relationship between the light source required for optical microanalysis and thickness of bottom cladding is simulated based on MATLAB,the results show that,for the structure with 310 nm silicon nitride as bottom base core,the contrast rate could exceeds 0.1 using 620 nm orange light source when the thickness of bottom cladding is 2000 nm,as well as using 550 nm green light source when the thickness of bottom cladding is 2670 nm.For the graphene with defects,the Raman spectroscopy analysis for a non-defective region viewed under microscopy is analysised,the results show that the local characteristics of Raman spectroscopy could be confirmed,and the feasibility of the test method proposed could be confirmed combined with the simulation results of microscopy analysis.