Fabrication And Doping Of Detectors Based On Mechanically Stripped Graphene FET

Since 2004,graphene,a new type of two-dimensional planar crystal,has many unique applications due to its excellent physical and electrical properties.And graphene exhibits new research directions for the development of all-carbon-based electronic circuits,electronic devices and semiconductor electronic information technology in the future.In this dissertation,we prepare graphene by mechanical exfoliation,study the electrical properties of the prepared GFETs and further investigate the doping of graphene and the photo-response mechanism of the photodetectors.A single-layer graphene is prepared on SiO₂/Si substrate by mechanical exfoliation method,and the size is 15²5?m.The preliminary layer number and orientation of graphene were determined by metallographic microscopy.and then by Raman spectroscopy,we can obtain that I_G/I_2D<1/2 to single-layer graphene and I_G/I_2DD close to 1 to bilayer graphene.The number of layer graphene layers and defects were characterized.The preparation of a back gate structure GFET is accomplished by photolithography and metal deposition using a negative lift-off approach.Electrical tests are performed on the prepared GFETs to determine if the device has formed a complete ohmic contact and to determine the change in graphene conductivity based on the Id-Vd curve;according to the shape of the Id-Vg curve,the electrical properties of the graphene can be divided into the following two types.:Bipolar Id-Vg curve,electron and hole mobility are 107 cm²V^-1s^-11 and 105 cm²V^-1s^-1,respectively;unipolar Id-Vg curve,hole mobility is 691 cm²V^-1s^-1.Adsorption of air molecules on graphene will produce P-type doping of graphene.Then,the aqueous GFET device is doped with an aqueous ammonia solution to realize surface modification of N-type graphene.Ammonia doping of graphene is physical adsorption doping.This doping method is very unstable,and graphene can also return to its original state.Combining Cu InS₂/ZnS quantum dot materials with different peak wavelengths and graphene,utilizing the high mobility of graphene,the high light-absorbing ability of CuInS₂/ZnS quantum dots and the long carrier recombination time,resulting in a high photoconductivity gain and high-light-responsive devices were prepared.The devices coated with Cu_0.2In_0.8S₂/ZnS QDs with a peak wavelength of 710 nm have a strong response to light at 405 nm,520 nm,and 650 nm,and the response currents are approximately in the order of ten microamperes.942 A/W,5299 A/W,250000 A/W.The device responsivity of spin-coated Cu_0.14In_0.86S₂/ZnS QDs with a peak wavelength of630 nm was 1.18×10³ A/W and 1.76×10⁴ A/W at 405 nm and 520 nm,respectively.For the device fabricated by combining Cu_0.2In_0.8S₂/ZnS at a peak absorption wavelength of710 nm with graphene,the corresponding photoconductive gain reaches 925930 at 650nm,and the lifetime of photogenerated carriers in the quantum dot is 66.138?s.