Research On Novel Hot Carrier Devices Based On Two-dimensional Materials And Van Der Waals Heterostructures

The traditional semiconductor technology has encountered the bottleneck as the Moore's law is approaching its limit.The essence of pushing the semiconductor technology towards Post-Moore Era is how to develop innovatory mechanisms,new materials,and novel configurations to balance the trade-off among energy,cost and performances during the scaling down.With the guideline of Beyond CMOS,we considered three aspects including novel physical mechanism,materials platform,and device structure to develop our research topic.The purposes of this thesis are analyzing the mechanism of hot-carrier devices,improving their performances,and extending their functionalities.In terms of materials platfrom,we focus on the two-dimensional materials.As for physical mechanism,we mainly study the hot-carriers-related phenomenon.All of the solid-state functional devices in our study of interest are based on van der Waals(vd W)heterostructures.This thesis mainly introduces four kinds of hot-carrier devices.The details are as below:(1)The thesis first studies the infrared photodetector based on a plasmonic nanostructure/graphene/boron nitride(BN)/graphene heterostructure.We mainly focus on the physical mechanism and explore the excitation of the ultra-hot carriers in graphene by utilizing the surface plasmonic.We find out that the excitation of ultra-hot carriers significantly breaks the wavelength limit of internal photoelectric effect and realizes sub-bandgap photo-response.Furthermore,we have studied the physical mechanism of ultra-hot carriers and the novel negative differential photo-response.(2)The second device studied in this thesis is the room-temperature valleytronic transistor based on a chiral plasmonic nanostructure/monolayer molybdenum sulfide(Mo S2)heterostructure.Aiming at exploring non-charge information carriers,we proposed and realized a solid-state valleytronic device which enables a full sequence of generating,propagating,detecting,and manipulating valley information at room temperature.The valley polarization is generated by the chiral plasmonic nanostructure,followed by the injection of hot carriers into a certain valley.Through the pseudomagnetic field induced by the opposite Berry curvature in different valleys,the valley polarization is read out as Hall voltage,which can be controlled by the gate voltage.(3)The third device introduced in this thesis is an on-chip infrared polarimeter based on a graphene/plasmonic metasurface/silicon heterostructure.To realize multifunctional integration,we design a photodetector with four sub-pixels.This photodetector can simultaneously obtain the intensity and polarization information of the incident light.The polarimetry is realized by designing plasmonic metasurfaces with different chiralities and orientations.The silicon-based Schottky junction configuration realizes the efficient separation of photo-excited electron-hole pairs.This device successfully demonstrates the polarimetry of the polarized incident light.(4)Finally,the thesis introduces a hot electron transistor(HET)based on a graphene/tungsten selenide(WSe2)/graphene/BN/graphene five-layer heterostructure.We have designed and experimentally demonstrated the first all-two-dimensional-material based HET,which obtains a high common-base hot carrier collection efficiency approaching the theoretical limit.In addition,we also have studied the hot carrier spectroscopy by using this HET as an ideal platform.The systematic research in this thesis indicates that the two-dimensional materials not only offer high-quality interface with large degree of freedom in hetero-assembling,but also endow the device with novel characteristics and good performances that is challenging for their bulk counterparts.This thesis demonstrates the promising potential of two-dimensional materials and their vd W heterostructures in the future semiconductor technology.