Study Of The New Type Graphite/Silica/Silicon Photodetector

Photodetectors are an important medium for converting light into electricity to obtain optical information.Photodetectors have been widely used in military,medical,plant production and other fields because of having advantages of small size,low power consumption and high sensitivity.Recently,the researches and reports on silicon-based photodetectors have gradually increased because silicon materials have the advantages of easy production,low price,and abundant resources.Silicon materials have become important materials for the manufacture of photodetectors.The silicon based photodetectors have developed a variety of structures for different applications including silicon-based p-n junction photodetectors,silicon-based MSM photodetectors and silicon-based PIN photodetectors.This thesis employees the n-Si as the substrate.Choosing graphite material in order to form a heterojunction photodetector with n-Si.The structure and electrical characteristics of the photodetector are systematically studied,mainly including the following two aspects:First,preparing a graphite/silica/silicon heterojunction photodetector with graphite material and n-Si.As an easily conductive sheet-like material,graphite has a certain light transmittance and its work function is greater than the n-Si materials.This thesis combines graphite with n-Si to make a photodetector.In the third chapter of this thesis,graphite is combined with silicon dioxide on the surface of n-Si by mechanical exfoliation.Scanning Electron Microscopy,Transmission Electron Microscopy,Electron Energy Spectroscopy,Raman spectrometer and test are used to analyze the sample's morphology,crystal structure,and elemental composition.Studying the response of the photodetector under different wavelength conditions.It is found that the output photovoltaic voltage and photocurrent of the detector increases with the increase of the laser wavelength,and reaches the maximum photovoltaic voltage(107m V)and the maximum photocurrent(3.6?A)under the condition of900 nm infrared light irradiation.The large wavelength response range makes this photodetector suitable for both visible and infrared light.The graphite/silica/silicon photodetector performance regulation.The fourth chapter of this thesis uses dry oxygen method to grow silicon dioxide films with different thicknesses on the surface of n-Si and studying the effect of silicon dioxide thickness on the performance of the detector.Studies show that as the thickness of the silicon dioxide layer increases,the performance of the photodetector changes significantly under the same test conditions.Whenthe thickness of the silicon dioxide layer is about 3nm,the photovoltaic voltage of the detector is 108 m V.When the thickness of the silicon dioxide layer is 14 nm,the photovoltaic voltage of the detector reaches a peak of 138 m V.Through theoretical analysis and modeling of the heterojunction structure,it is also found that the introduction of the silicon dioxide insulating layer can effectively increase the barrier height of the graphite/silicon heterojunction,thereby reducing the dark current of the photodetector and improving the performance.