Mechanism Of Silicon-based GFET And Application In Terahertz Waves Modulation

Terahertz waves is considered to the hotspots in the current scarcity of wireless communication band resources.The system with terahertz wave as the communication carrier has attracted the attention of relevant research institutes due to its high transmission rate,large bandwidth and strong anti-interference.After the terahertz source and detector problems are resolved,terahertz waves signal modulator as one of the key functional devices of terahertz communication has become a research hotspot.This thesis combines the excellent properties of two-dimensional graphene,graphene field effect transistor terahertz wave modulator and a flexible bismuth nanorods/graphene terahertz wave modulator were prepared.We first describe the method of wet transfer CVD copper-based single-layer graphene film,transfer process optimized for the problems in the experimental process,thereby obtaining a high quality single layer graphene film.A back-gate graphene field effect transistor is prepared by growing HfO₂ gate dielectric film based on pulsed laser deposition,film prepared by this method has poor quality and low breakdown voltage,and cannot effectively adjust the carrier concentration in the graphene film in the range of available gate voltage,and the terahertz modulation effect is poor.Therefore,we have prepared a high quality HfO₂ film using an atomic layer deposition system,breakdown voltage can reach 40 V or more when the thickness is 60 nm,effectively control the carrier concentration in graphene film within its available gate voltage range,and the HfO₂ is high-k material,and the FET prepared based on this has a large trans conductance.By testing our prepared graphene FET terahertz wave modulator,the terahertz wave can modulated in the range of 0.2 to 1.2 THz with a modulation depth of up to 19%and a modulation speed of 135 KHz.Finally,we prepared a flexible bismuth nanorods/graphene terahertz wave modulator.Enhance its response to infrared light by interacting with a nanorods and an open-band graphene film.The purpose of modulating the terahertz wave achieved by optical excitation,and the modulator has a maximum modulation depth of 15.7%in the range of0.2 to 1.2 THz.Its structure has lower insertion loss for terahertz waves than conventional silicon-based modulators.Provide some new ideas for the research and development of terahertz wave modulation.