Performance Research On Semimetal Materials Heterostructure Broadband Photodetectors

The innovation of broadband photodetector is closely related to the discovery and application of new-type narrow/zero bandgap optoelectronic materials.Since successful fabrication of graphene（Gr）infrared photodetector,the feasibility of using semimetal materials to construct high-speed broadband photodetectors operating at room temperature have been gradually confirmed.With the confirmation of topological quantum states（such as Dirac fermions and Weyl fermions）from theoretical and experimental in some substances,novel quantum materials have ushered in an age of vigorous development.The research category of this material system has expanded from graphene to multiple branches including Dirac/Weyl semimetal,Weyl semiconductor and Topological insulator.Since they can exhibit the semimetal properties due to extraordinary topological quantum states,some researchers also call them semimetal quantum materials.The novel physical performance of this material system（such as,ultra-high charge mobility,strong light-matter interaction,excellent broad spectral absorption,and topological zero/narrow bandgap band structure,etc.）makes it promise to be used in mid/far infrared broadband photodetection field.Besides,it has great potential to break the performance limitations of traditional infrared photodetectors,providing ideal candidate and new development opportunity to exploit high-speed broadband photodetectors at room temperature.In this dissertation,several kinds of representative semimetal materials possessed quantum properties are selected as the main research objects,including cadmium arsenide（Cd₃As₂）,zinc-doped cadmium arsenide((Cd_1-xZn_x)₃As₂,ZCA),Tellurium（Te）and Bismuth Telluride（Bi₂Te₃）.In view of the research status and existed scientific problems in broadband photodetection fields,the photoelectric properties of fabricated semimetal materials-based photodetectors are investigated by combined with material preparation method,device structure optimization strategy and photo-detection mechanism.The main research contents can be divided into four parts as follows:1.Based on three-dimensional（3D）Dirac semimetal Cd₃As₂ nanoplates grown by physical vapor transport（PVT）,Cd₃As₂ based heterojunction photodetectors（Cd₃As₂/copper phthalocyanine（Cu Pc）and Cd₃As₂/tungsten sulfide（WS₂）heterojunction）were constructed,and its photoelectric performance from visible to near-infrared waveband were investigated.Due to formation of heterojunction,the dark current noise of Cd₃As₂/Cu Pc photodetector has been reduced to a certain extent,among which the normalized detectivity（D*）at 808 nm is about 7.83×10¹⁰ Jones.Furthermore,by integrating Cd₃As₂ nanoplate with two-dimensional（2D）WS₂,the fabricated Cd₃As₂/WS₂ van der waals heterojunction photodetector has a better signal-to-noise ratio（SNR）.The maximum value of D*at 808 nm light can reach 2.1×10¹⁴ Jones,and other performance parameters such as responsivity（R_i）and response time（τ）have also been significantly optimized.This work provides a reference strategy to suppress the dark current and improve SNR of 3D Dirac semimetal materials-based photodetectors.2.To achieve the arrayable photodetection target using 3D Dirac semi-metal material,the surface charge concentration of Cd₃As₂thin film was regulated by doping zinc（Zn）atom,which grown by molecular beam epitaxy（MBE）method.Based on zinc doped cadmium arsenide（ZCA）film with better photoelectric property,the detection performance of ZCA film heterostructure linear array photodetectors were investigated.The constructed ZCA/In₂Se₃ heterojunction photodetector can perform detection function at 0 V,among which the optimal D*at 450 nm is about 4.55×10¹¹Jones.Moreover,the fabricated 3D Dirac semimetal ZCA/Sb₂Se₃ back-to-back（BTB）heterojunction photodetector exhibits relatively high SNR closed to 10⁴ even under large bias,and its D*is up to 5.2×10¹² Jones at 450 nm.In additions,the device also achieved high-speed broadband photodetection target from visible to mid-infrared wavebands（450 nm-4500nm）at room temperature.3.Based on semimetal tellurium（Te）thin film grown by MBE,the photoelectric properties of Te-based heterostructure film photodetectors were investigated.The fabricated Te/Sb₂Se₃ photodetector can realize broadband detection target from visible to mid-infrared wavebands（405-4500 nm）,and corresponding maximum value of R_i and D*at 808 nm could reach to 110.8 A/W and 2.09×10¹³ Jones,respectively.Furthermore,by using C₆₀ as charge-regulation medium,the Te/C₆₀/Sb₂Se₃ heterostructure photodetector exhibits a bidirectional photocurrent output phenomenon depended on wavelength and optical power density,which provides a reference material system to develop light-controlled multifunctional optoelectronic logic devices in future.4.To effectively realize the target of high speed and broadband photodetection at room temperature using Te semimetal-based compounds,the photoelectric properties of2D telluride atomic crystal Bi₂Te₃-based heterojunction photodetector was investigated.After epitaxial large-area and high-quality Bi₂Te₃ thin film on GaAs（111）B substrate by MBE,a graphene（Gr）/Bi₂Te₃/GaAs heterojunction photodetector was constructed using graphene as charge collection medium.The fabricated device can realize fast photo-response speed on the order of microseconds and broadband detection performance from visible to mid-infrared waveband at room temperature,which provides an effective reference paradigm to develop new-type high speed broadband photodetector based on two-dimensional telluride quantum materials.In summary,this dissertation focuses on the application of new-type semimetal materials in broadband detection field.By combining with other semiconductor materials,the semimetal materials heterostructure photodetectors have been developed,which achieve the high-speed broadband photoelectric detection target from visible to mid-infrared band at room-temperature.The related works provide reference approach for the construction of novel infrared broadband photodetector.