High Performance Broadband And Dual-mode Photodetector Based On Fluorographene

Photodetector is a kind of electronic device that can transfer optical signal to electric signal and has significant application in fields of industrial production,fiber optic communication,remote sensing and image sensing.Graphene is a kind of well-performance 2D material and is widely used as photodetector.However,the bandgap of instinct graphene is 0 eV and its ability of light absorption is weak.Therefore,fluorination was used to open up the bandgap of graphene and enhance the ability of light absorption for photodetector application.There are many kinds of photodetectors and each of them has different advantages and disadvantages.Herein,a dual-mode photodetector has been successfully prepared,which can work at both photoconductive and photodiode modes and can make complementary advantages.The specific results are as follows:1.Copper-based graphene has been synthesized through the chemical vapor deposition(CVD)method.Raman spectrum verified that the as-synthesized graphene was high quality with less defects.Reactive ion etching(RIE)was used to dope graphene using the doping source SF6 gas.Raman spectrum and X-ray photoelectron spectra showed the apparent sp3 hybrid fluorocarbon bond,proving the doping is successful.2.Fluorographene/silicon dual mode photodetector was prepared using lithography process,which is well compatible to traditional silicon-based CMOS process.AlOx passivation layer was prepared using electron beam deposition.When the photodetector works at photoconductive mode,it has obvious photoresponse at wavelengths of 200-1550 nm,which indicates it is a broadband photodetector.When the driving bias is 5 V3 the responsivity of the photoconductive photodetector is 1.9×107 A/W under 650 nm light illumination.The relative detectivity is calculated as 4.0×1012 Jones,which indicates that the photodetector is sensitive to weak light.And the responsivity of 1550 nm communication band is 39 A/W,which is two orders higher than intrinsic graphene/silicon photoconductive photodetector.The rise time/fall time of the photodetector is 5.2 ms/5.9 ms.3.When the photodetector is working at photodiode mode,it has obvious rectification effect,the rectification ratio of the photodetector is 460.The photodetector has feature of self-driven,which indicates it can work without driving bias.Responsivity of the photodiode photodetector under 650 um light illumination without driving bias is 0.33 A/W and on/off ratio is 2.0×105,detectivity is 2.3×1011.Jones.When the photodetector is working at photodiode mode,it has feature of fast photo response.3 dB bandwidth is 11.9 kHz and rise time/fall time is 6.3 ?s/9.7 ?s,which indicates that the photodiode photodetector is suitable for fast photo detection.In summary,the fluorographene/silicon dual-mode photodetector can achieve complementary advantages of broadband,high responsivity,high detectivity and fast speed.At last,first principles calculation method was used to calculate density of state and energy band diagram.Theoretical analysis was used to analyze the open-up condition of bandgap of fluorographene and the influence of semiconductor absorption.