Research On Terahertz Detectors Based On Low-dimensional Materials

Terahertz waves occupy a unique position in the electromagnetic spectrum,with frequencies between microwave and infrared.With the maturity of electronic technology and semiconductor technology,terahertz technology has been rapidly developed in military,high-speed communications,security imaging,astronomical remote sensing and biomedical fields.The terahertz detector is one of the important components in the application of terahertz technology.Its function is to convert the terahertz signal into electrical signal,so as to detect the terahertz wave information.In recent years,the development of terahertz detectors has made breakthrough progress,but there are still some common problems in terahertz detectors.At present,refrigerated terahertz detectors have the advantages of high sensitivity and low noise equivalent power,but their cost is high and their volume is large.The terahertz detector operating at room temperature has high noise equivalent power and low sensitivity.It is a long-term goal of the development of terahertz detection technology to explore a highly sensitive,low-cost,miniaturized terahertz detector operating at room temperature.In view of the above problems,this paper mainly studied Highly Sensitive Graphene Terahertz Detection Driven by two-dimensional Ferroelectrics and Weyl semimetal Co₃Sn₂S₂Terahertz detector.It includes device antenna structure design and numerical simulation,device fabrication and processing,device terahertz photoelectric properties characterization and mechanism analysis,and room temperature terahertz transmission imaging application.The innovation and research contents of this paper are as follows:1.Graphene has excellent properties such as low defect density,easy large-area transfer and extremely high carrier mobility.However,the zero-bandgap band structure of graphene leads to a short lifetime of photogenerated carriers,which restricts its application in highly sensitive photodetectors.In this work,a two-dimensional ferroelectric material Cu In P₂S₆(CIPS)was used as a top gate to regulate the photoelectric properties of graphene.We applied a gate voltage to the CIPS,and through forward and reverse scanning,obvious hysteresis curves were observed to regulate the carrier concentration of graphene.By introducing the butterfly antenna structure into the device,the terahertz light source is coupled into the channel to achieve super electromagnetic compression,and the asymmetric gate structure is designed to introduce the asymmetry of electric field distribution,so as to explore the possibility of improving the sensitivity of graphene terahertz detector.The detection mechanism of photothermoelectric effect and plasma wave self-mixing effect of devices was analyzed.The stability and room temperature terahertz imaging ability of the device are verified.The experimental results show that the responsivity of detector at room temperature reaches 0.5 A/W at 0.12 THz,with the response time of 1.67?s and the noise equivalent power(NEP)of 0.81 n W/Hz^1/2under a bias voltage of 40 m V and a gate voltage of 2.12 V.At 0.29 THz,the responsivity is determined to be 0.12 A/W,and a NEP is 1.78 n W/Hz^1/2.This work demonstrates the great potential of two-dimensional ferroelectric heterostuctures at THz band.2.Co₃Sn₂S₂is a new Weyl semimetal with special topological surface states,which makes it have the characteristics of large wavelength range and fast response speed in the field of long wave detection.In this work,we mainly designed and prepared the room temperature terahertz detector based on Co₃Sn₂S₂material.A wideband frequency butterfly antenna is designed to enhance the terahertz electric field by coupling terahertz radiation.When the bias voltage is zero,the response rate is 0.18 A/W at 0.29 THz band,and the response time is 3.97?s.Moreover,the transmission imaging of metal ring is realized at room temperature.This indicates that Co₃Sn₂S₂is an ideal material for realizing high-performance photoelectric detection system in terahertz band.