Research On Functionalization Of Graphene Photodetector

Graphene is a zero-bandgap semiconductor with the properties of broadband absorption and ultra-high carrier mobility,which makes graphene has a good prospect in the field of photodetection.However,as a photosensitive material of photodetector,graphene has two intrinsic shortcomings,one is only 2.3% absorption of light,makes the external quantum efficiency of graphene-based photodetector is low;another one is the short lifetime of the energetic exciton of graphene,which means the photogenerated electron-hole pairs will recombine together rapidly after it produced and can not separate effectively to form photocurrent.Therefore,the functionalization of graphene photodetector is very necessary,which means improve the light absorptivity or exciton lifetime of the device and the photodetection performance based on the existing.In this paper,a graphene photodetector was fabricated by using PbS quantum dot layer-by-layer spin-coating method,and a high-responsivity,broadband photodetector was fabricated.First,the transfer process and mechanical exfoliation of graphene was studied.Graphene grown on Cu foil by chemical vapor deposition was transferred to a silicon substrate.Then the transferred graphene and the mechanical exfoliated graphene were used as channel materials to fabricate a field-effect transistor by photolithography,etching and other processes.The mechanism of charge transfer between ligand and quantum dot was studied by modulating the type of ligand and the number of spin-coated layers,followed by measuring the photoelectric properties of the devices.Finally,the application of graphene in the field of imaging was explored.A 128 × 1 linear array photodetector was fabricated.The pixel pitch and size of the device were in accordance with the actual package and wafer test requirements.Each pixel is a graphene-quantum dot composite photodetector,and the uniformity and stability of the linear array device are well characterized by photoelectric test.The method of quantum dot functionalized graphene used in this paper is simple,mild and can be carried out at room temperature and in the atmosphere,and can be prepared on a large scale.The photodetector prepared by this method has the advantages of high responsivity,broadband and fast response,which makes the functionalized graphene photodetector have great potential in the field of photoelectric imaging.