Research On Terahertz Source Characteristics Based On Double Top Gate Graphene Field Effect Transisto

Terahertz wave is between microwave and infrared light.It has important academic value and application potential due to its excellent characteristics such as high transmittance,low energy,and broadband.It has not been effectively developed for a long time due to the lack of related source devices.The research and development of terahertz radiation sources is the key to the market for terahertz technology.The current urgent need in the field of terahertz radiation research is high-power small solid-state terahertz sources operating at room temperature.Graphene has received extensive attention due to its unique optoelectronic properties in the terahertz frequency band,and it is expected that this new material can be used to achieve terahertz radiation.In this paper,the study of graphene-based terahertz radiation sources is carried out,the terahertz radiation source model with graphene p-n junction structure is designed,and the following work is done in view of the working mechanism,radiation mechanism and radiation performance of the device:1.A graphene field effect transistor with double-top gate structure is proposed,this device has p-n junction characteristics.The current model of the device is established by using the gradually varying channel approximation method,and the output characteristics and transfer characteristic curves of the device are drawn.The obtained results show that the conductivity type of the channel region of this device is determined by the bias voltage,and the gate voltage determines the height of the p-n junction barrier.When the gate voltage is large,a negative transconductance phenomenon will occur to suppress the growth of current.The transmission spectrum of double-top gate graphene nanoribbon FET was also analyzed by ATK software,and the influence of the gate voltage,the gate gap and the dielectric constant of the dielectric layer on the device transport was studied.2.Using the hydrodynamic equations and two-dimensional Poisson equations that control the carrier transport in graphene,the dynamic process of the i-zone in the graphene p-i-n junction under a forward bias voltage is studied,by solving the equation,the spatial distribution of quasi Fermi energy level and energy band edge profile of graphene under positive bias are obtained.The results show that the induced band gap of graphene can reach tens of me V under external electric field,which is enough to radiate energy in the terahertz band.The dynamic conductivity of graphene in the terahertz frequency band is also calculated,and the influence of different parameters on the dynamic conductivity is studied.The results show that the dynamic conductivity of graphene under electric pumping is negative in a wide terahertz range,indicating that the inter-band radiation in this range is greater than the intra-band absorption,and this result also indicates that graphene has the ability to radiate terahertz.3.The electron-hole recombination mechanism in graphene is introduced,the Auger rate of graphene on Si O₂,Hf O₂ and Si C three polar substrates is studied,and the influence of temperature and carrier concentration on the auger rate is discussed.The results obtained help to understand the actual luminous efficiency of graphene.4.The structure of the distributed Bragg reflection grating is designed to be combined with the double-top gate graphene field effect transistor as a complete terahertz radiation source to realize the generation,frequency selection and amplification of terahertz photons.According to the device characteristics,based on the semiconductor laser’s rate equation theory,establishing simulation system with Simulink,the output characteristics of the device are analyzed,and the impact of important parameters such as injection current and ambient temperature on the output performance of the device is studied.