Mechanism Study Of Graphene-based Terahertz Radiation Source

Terahertz waves are located in the region between microwave and infrared,and have broad scientific application prospects due to their advantages of low energy,strong transmission,and broadband.Terahertz source is a key technology for terahertz engineering applications.The development of a miniaturized,room-temperature,and high-power terahertz source is an urgent need for the development of terahertz science and technology.Graphene has excellent electronic and optical characteristics in the terahertz frequency range,and it is expected to be a great material that can be used for a new type of terahertz source.This paper studies the mechanism of graphene generating terahertz radiation,and the works is as follows:1.The working principle of electrically pumped double-top gate graphene field-effect transistor to generate terahertz photons is analysed,and the relationships between the integrated conductance of graphene and factors such as bias voltage,relaxation time,gate voltage and temperature are obtained.The terahertz radiation mechanism of optically pumped monolayer graphene and electrically and optically pumped graphene plasma is presented.The integrated conductance of optically pumped graphene and the absorption and propagation coefficients of optically and electrically pumped graphene plasma are investigated.2.Molecular models are developed using ATK software to study the energy band structure of graphene in contact with metals and dielectric materials.Graphene forms P-type doping when in contact with gold,platinum and silicon dioxide;when in contact with dielectric materials such as alumina,silicon nitride and hafnium dioxide,graphene maintains its original energy band properties.The graphene is characterized by Raman spectroscopy and SEM,and the bottom-gate GFETs with Cr/Au as the drain and source electrodes and SiO₂/Si as the substrate are tested to obtain the output and transfer characteristic curves,which verify the P-type doping and bipolar properties of graphene.3.A double-top-gated graphene nanoribbon FET device is constructed,the PN junction characteristics of the device are verified,the transmission spectrum of the device is analysed,and the effects of gate voltage,gate gap and dielectric layer dielectric constant on the device transport are investigated.4.An optical cavity with distributed feedback Bragg structure is proposed,which can be used as a graphene homojunction terahertz semiconductor laser in combination with the double-top-gate graphene FET.The output characteristics of the distributed feedback double-top-gate graphene FET are analysed using the rate equation,and the effects of bias current,optical gain coefficient and carrier lifetime on the output power of the device are investigated.