Research Of Terahertz Modulator Based On Graphene Field Effect Transistor Structure

In recent years, THz as an emerging electromagnetic researching waveband, its relevant functional device THz wave modulators have been very innovative researching. Now the theory and device in terahertz spectrum is not mature, and there are some deficiencies of the modulators which were prepared, such as low modulation speed, small modulation depth, because of what the rapid development applications in terahertz communications and terahertz imaging were seriously restricted. Two-dimensional material graphene has a significant response on terahertz wave, the composite structure artificial electromagnetic metamaterials with graphene, which shows a great potential application in terahertz communications and terahertz imaging systems.This paper first introduces the structure, properties and general transfer process of graphene, then we done two optimized researches in graphene general transfer process according to the result of experiment. And we also discuss in detail on the preparation of the back-gate graphene field effect transistor which could be showed excellent electrical performance, including structure, principle and preparation of transistor, electrical performance test, and also graphene channel doping. Through constantly exploring the preparation process of graphene transistors, constantly we optimized and strictly controlled the process flow and process parameters. Last we prepared the graphene transistor with excellent performance. Others, we also analyze the substrate cleaning, basic process exploring, DFM and XRD characterization of Al₂O₃ thin film, the significance of transistor basic parameters, and transistor test methods.Finally, the metamaterial simulation and the terahertz testing systems are introduced in this paper. Based on the structure, process and test results of graphene field effect transistors, combined with electromagnetic metamaterial structure, we designed the terahertz wave modulator based on back-gate GFET structure frequency selectively. Then we proposed an optimization scheme with another terahertz modulator based on back-gate GFET structure, which contains array graphene. This paper shows the principle, structures and preparation of the two modulators, then the two have been tested with our own time-domain spectrum system and space transmission dynamic system. Respectively, the two terahertz modulators were tested with results 17.7% and 26% of the modulation depth,and also showing a 3 dB operation bandwidth of 50 kHz and 84.5 kHz, the second was made a better modulation performance.