Contrallable Synthesis Of 2D TMDC And Their Silicon Integration Photodetector

Photodetectors are pivotal components in the modern miniaturized electronic industry,which have been applied in agriculture,industry,and military.In traditional schemes,various photosensitive materials have been expoited and applied to detect ultraviolet,visible,near infrared,mid infrared,and far infrared light,such as Si,Ge,In Ga As,In Sb,Hg Cd Te,superlattice,and so on.In recent years,higher performances of photodetector have been put forward,owing to the rise of artificial intelligence,internet of things.However,conventional materials suffer from band-gap limitation,rigidity,or lattice mismatch,which are difficult to meet the needs of the next-generation devices with high sensitive,multiband adjustable,silicon-based integrated,lightweight and low-cost intelligent sensing.Thus,the update of opelectronic information devices depends on the breakthrough of materials.Two dimisional(2D)materials have become the frontier research focus in the field of materials research duo to its tunable carrier concentration and conduction type,strong interaction with light,flexibility.And it is easy to construct functional artificial heterostructures of different layered compunds due to there is no dangling bond.And it is widely accepted that 2D materials will play an important role in the applications of next-generation nanoelectronics,optoelectronics devices.Although scientists have made great progress in the synthesis of 2D materials and exploration of device performance,it has not been completely clear about the large-scale application and the mechanism of photoresponse.This dissertation focuses on the synthesis of two-dimensional TMDC films and based on 2D-Si heterojunction photodetectors.We manily studied the growth law and key technologies of synthesis of 2D materials,and the photoelectric transport properties and physical mechanism of 2D-Si heterojunction photodetector.The main contents are summarized as follows:1.The controllable synthesis of TMDC films by CVD was studied.The transition metal precursor and chalcogenide precursor were placed in two separate quartz tube by a self-designed CVD growth system,which can avoid the transition metal precursor being sulfurized into refractory transition metal chalcogenide before evaporation in the tranditional CVD method,and ensure the continuous and stable supply of transition metal precursor.It means that a modulation growth of TMDC film can be realized by controlling the growth time.Monolayer,bilayer,trilayer and multilayer MoS₂ film was grown on removable sapphire substrate,and the monolayer MoS₂ film showed obvious epitaxial growth characteristics.In addition,the method is also suitable for other TMDC,such as MoSe₂,WS₂,and WSe₂.It is expected to expand the synthesis methods for other 2D materials by this method and develop large-scale and integrated applications.2.The electrical and optical properties of MoS₂-Si heterojunction devices were studied.MoS₂-Sidevice is successfully fabricated by transferring MoS₂ onto etched Siby wet transfer method.The device works in avalanche breakdown regime under large bias voltage due to the breakdown of one of two opposite semiconductor junctions formed between MoS₂ and Si.And the characteristic of avalanche breakdown can be adjusted by the junction width and thickness of MoS₂ film.The device exhibits a wide spectral response ranging from 200 to 1550 nm,and shows a responsivity of 5 A/W,specific detectivity of 2.8×10¹²Jones,response time of 84.3 ms and optical switch ratio of current of 10³ under 800 nm with 6.34 m W/cm².In addition,the visible and near-infrared imagings resuls show that the device presents good single-pixel imaging function.It expands the application of TMDC films in functional device.3.The optical response characteristics in different regions and the influence of interface layer on the photoelectric properties for the Gr-Si-based vertical devices were studied.It is found that the edge region of Gr-Sijunction is the most sensitive to light.A smaller photocurrent is detected for a closer distance to the center in the Gr-Siregion or a farther distance to the center in the Gr-SiO₂-Siregion.In addition,by introducing SiO₂,Al₂O₃,WO₃ and WS₂ interface layers between Gr and Si,the optoelectric properties is improved by an order of magnitude due to the formation of hole barrier layer between the interface layer and Si,which increases the recombination time of photogenerated holes and electrons and photogain.The results indicate that the appropriate size of the device structure and the introduction of interface layer are effective means to improve the performance of Gr-Si-based heterostructure photodetectors.4.The working mechanism of Gr-WS₂-Si heterojunction photodetector and the influence of the thickness of interface layer WS₂ on the device performance were studied and analyzed.The thickness of WS₂ film affects the light transmittance,the number of bound states,the series resistance,and the Schottky barrier formed by Gr and Si,and further affects the photoresponsivity,specific detectivity and response speed of Gr-WS₂-Siphotodetectors.The device shows a maxmun photoresponsivity of8.96×10⁴ A/W and high specific detectivity of 8.86×10¹¹ Jones at 690 nm when WS₂is 10.9 nm,which is the highest responsivity based Gr-Siphotodetector reported at present.In addition,the device shows a wide spectrum response from 400 to 1800 nm with a hundreds m A/W photoresponsivity at 1550 nm owing to the type-II interlayer excitation.The results prove a great potential of Gr-WS₂-Siphotodetector for the application in wide spectrum and high performance.