Controlled Growth Of Wafer-Scale 2D MoTe₂ Layer And Application In Infrared Photodetector

Broadband infrared photodetectors with integratable capabilities have good applications in target recognition,imaging,remote monitoring,gas sensing and other fields.Currently,commercial infrared photodetectors are mostly based on mature narrow-bandgap semiconductor materials,such as in the near-infrared（NIR）range,silicon（Si）and indium gallium arsenide（In Ga As）-based photodetectors are mainly used.Mercury cadmium telluride（Hg Cd Te）,indium antimonide（In Sb）,lead selenide（Pb Se）,superlattices and quantum wells are mainly used in the mid-infrared（MIR）.However,conventional infrared photodetectors are still facing great challenges for further application.The low temperature working conditions cause high-cost、high-power consumption.At the same time,the preparation of these materials require complex fabrication techniques and time-consuming procedures.Two-dimensional transition metal chalcogenide（TMDs）materials are not limited by chemical bonds and lattice matching,can be integrated with other semiconductor materials;Two-dimensional TMDs materials have characteristics of atomic layer thickness,which leads to the quantum confinement effect,improving the absorption efficiency of light;The band gap of the two-dimensional TMDs can be adjusted by controlling the thickness,making it possible to detect wider spectral range.Some two-dimensional TMDs with high quality and large area have been synthesized,providing good materials for array devices.Two-dimensional transition metal chalcogenide are usually combined with three-dimensional semiconductors to form two-dimensional/three-dimensional（2D/3D）mixed-dimensional heterojunctions in order to enhance light absorption and improve the separation efficiency of photogenerated carriers.Based on the above analysis,this thesis will use the van der Waals growth method to control the phase transition of 2D 1T’-MoTe₂（semi-metal）and 2D2H-MoTe₂（semiconductor）thin films and grow wafer-scale films.2D/3D mixed-dimensional van der Waals heterojunction photodetector were combined with three-dimensional semiconductors silicon（Si）and germanium（Ge）,respectively,and photoelectronic properties and infrared imaging of devices were systematically tested and analyzed.The specific research contents are as follows:1.Use the van der Waals growth method to control the phase transition of 2D1T’-MoTe₂and 2H-MoTe₂,and grow 2-inch wafer-scale 2D 1T’-MoTe₂and 2D2H-MoTe₂thin films.The samples were analyzed by Raman spectrometer（Raman）,X-Ray Diffractomer（XRD）,Electron Backscatter Diffractometer（EBSD）,X-ray Photoelectron Spectrometer（XPS）,Atomic Force Microscope（AFM）,Transmission Electron Microscope（TEM）and other instruments.2.1T’-MoTe₂/Si and 2H-MoTe₂/Si vertical heterojunction photodetectors were prepared by in-situ growth of two-dimensional 1T’-MoTe₂and 2H-MoTe₂films on SiO₂/Si substrates.The 1T’-MoTe₂/Si heterojunction infrared photodetector has self-powered wide-spectrum photodetection capability at room temperature.The device exhibits good photodetection performance with the responsivity of 526 m A/W,the external quantum efficiency of 66%,the specific detectivity of 5.3×10¹¹Jones,the response speed of 1.9/41.5μs and nanosecond tracking for pulsed optical signals.The specific detectivity are 4.75-2.8×10⁸Jones under wavelength range of 3.0-10.6μm.It has a good single-pixel infrared imaging capability for 10.6μm.In addition,8×81T’-MoTe₂/Si heterojunction array devices fabricated by using large-area 2D1T’-MoTe₂thin film,showing excellent performance in mid-infrared imaging at room temperature.3.The 1T’-MoTe₂was transferred to Ge by wet method to construct a1T’-MoTe₂/Ge van der Waals heterojunction photodetector,and its photoelectric properties were studied.1T’-MoTe₂/Ge exhibits self-powered wide-spectrum photodetection capability at room temperature.The responsivity and external quantum efficiency are 870 m A/W and 67%under 1550 nm,respectively.The responsivity are 0.31/0.12/0.056 m A/W under 3.0/4.6/10.6μm.