Study On Graphene/Silicon Heterostructure Photodetectors

High-performance photodetectors operating over a broad wavelength range from ultraviolet,visible to infrared are of scientific and technological importance for a wide range of applications.In this work,a photodetector based on van der Waals heterostructures of graphene and its fluorine-functionalized derivative is presented.It consistently shows broadband photo-response from ultraviolet(255nm)to mid-infrared(4.3 ?m)wavelengths,with three orders of magnitude enhanced responsivity compared to pristine graphene photodetectors.The broadband photodetection is attributed to the synergistic effects of the spatial non-uniform collective quantum confinement of sp2 domains,and the trapping of photo-excited charge carriers in the localized states in sp3 domains.Tunable photo-response has been achieved by controlling the nature of sp3 sites,the size and fraction of sp3/sp2 domains.In addition,the photo-response due to the different photo-excited charge carriers trapping time in sp2 and sp3 nano-domains has been distinguished.The proposed scheme paves the way toward implementing high-performance broadband graphene-based photodetectors.Furthermore,using fluorine functionalized CVD graphene(FG)as an example,and in contrast to traditional "hard-patterning" method of plasma etching,we demonstrate a solvent based"soft-patterning" strategy to enable its selective de-fluorination for the fabrication of graphene-FG lateral heterostructures with resolution down to 50 nm,in which the oxygen plasma etching process of patterning after graphene transfer is avoided and high quality surfaces are preserved through a physically continuous atomically thin sheet.which is critical for high performance photodetection,especially at high-speed domain.We further employ the fabricated lateral graphene heterostructures to demonstrate a high speed metal-semiconductor-metal photodetector(<10 ns response time),with a broadband response from deep UV(200nm)to near-infrared(1100 nm)range.Thanks to the high quality surface with much less defects obtained by "soft-patterning" strategy,we achieved a high deep-UV region photo-responsivity as well as the ultra-fast time response.Our strategy offers a unique and scalable method to realize continuous 2d lateral heterostructures,and underscores the significance of inspiring future designs for high speed optoelectronic devices.We also report a high-performance graphene/ultra-thin silicon metal-semiconductor-metal(MSM)ultraviolet(UV)photodetector,which benefits from the mechanical flexibility and high-percentage visible light rejection of ultra-thin silicon.In the near-and mid-UV spectral region,the proposed UV photodetector exhibits high photo-responsivity(0.47 A/W@ 3V),fast time response(1 ?s),high specific detectivity(2.5 ×1010 Jones),and UV/Vis rejection ratio of about 100,comparable to the state-of-the-art GaN and SiC Schottky photodetectors.The photodetector is semi-transparent,and its performance is stable after 1,000 bending cycles.Furthermore,we demonstrated UV imaging by replacing CCD array with the proposed graphene/silicon image sensor in a custom-designed digital camera.In addition,we also demonstrated printed black phosphorus ink based visible to near-infrared photodetector(BP/Gr/Si)with high responsivity.