Research On Photodetector Based On Graphene Composite Structure

At present,photodetector not only occupies an important position in industry and other fields,but also closely related to people’s life.It can convert optical signals into electrical signals for output.It is also an effective means for human beings to explore in visible light and a wider spectral range.Two dimensional materials are regarded as attractive materials for the preparation of new generation photodetectors because of their adjustable band gap,wide absorption spectrum,nano scale and flexibility.Graphene,as a representative of two-dimensional materials,has the outstanding advantages of zero band gap energy band structure and high carrier mobility.However,graphene has limited light absorption capacity and short carrier recombination life,so it is difficult to obtain high response of the photodetector.The coupling effect at the interface of graphene silicon composite structure determines the separation efficiency of photogenerated carriers,but the coupling effect at the interface of graphene silicon composite structure is not controllable.Therefore,exploring the optimal interface coupling of graphene composite structure is the focus of this thesis.In this thesis,ionic gel is used as dielectric layer to investigate the effect of the top gate voltage on the interface coupling effect of graphene silicon photodetectors.Through the software simulation,the law of the interface of the gate regulated composite structure is obtained,and the device of the model is prepared in the experiment to verify it.The results obtained are as follows:in the simulation,the top gate voltage can manipulate and control the carrier concentration and kind in graphene,change the Fermi level of graphene,and obtain a high built-in potential at graphene Silicon Schottky junction,which will be conducive to the separation and transmission of photogenerated carriers.In the simulation,the gain mechanism of graphene silicon composite photodetector is verified in the experiment.In the experiment,from visible light to infrared light,the optical gain under negative gate voltage is about 9 times higher than that without gate voltage,and the responsiveness of the device under gate voltage is also greatly improved.When V_tg=-3 V,the response is 1.1×10~4 A/W under 635 nm light source and 15 A/W under 1550 nm light source.The high response of the device is increased by about 5-8 times.The research results of this thesis have important reference significance for the interface coupling effect of graphene composite photodetector,and provide guidance for the gain mechanism of composite photodetector.