Research On Transport Mechanism,Photoelectric Properties,and Functional Application Of 2D/3D Semiconductor

With the development of integrated circuits,the computing power of chips continues to increase while energy consumption continues to decrease.However,upgrading the process can no longer significantly improve chip performance when the feature size reaches the nanometer level.To promote the further development of integrated circuit technology,researchers have researched and explored new electronic and optoelectronic devices based on new materials and structures in recent years.In terms of new materials,two-dimensional（2D）materials have unique physical properties,and remain high mobility at the atomic level.Since the interface of 2D materials has no dangling bonds,2D material devices experience less interface scattering.Therefore,2D materials show good application prospects in novel electronic devices and photodetectors.In terms of new structures,thanks to the fact that 2D materials are easy to form heterojunctions with other materials and the continuous development of semiconductor processing technology,researchers could design and fabricate 2D and 3D composite structures and heterojunction devices with various structures.On the one hand,it combines the advantages of 2D materials and 3D materials,which is conducive to the development of high-performance and multi-functional devices.On the other hand,applying two-dimensional materials to traditional semiconductor systems is beneficial to further promoting the development of two-dimensional material applications.This paper mainly focuses on 2D/3D heterostructure and heterojunction devices,analyze their basic performance as photodetectors and electronic devices,and realizes unique device functions such as polarization-sensitive detection,wavelength-distinguishing detection,reconfigurable devices,and novel logic devices.The main contents are as follows:1.Based on the infrared light absorption and polarized light sensitivity of black phosphorus（b P）,b P/Ge heterojunction photodetectors are designed,and the photoelectric characteristics of the devices are studied.Heterojunction devices formed by b P and different doping types of Ge are prepared,the influence of substrate doping on its electrical and optical properties is analyzed,and self-powered light detection and polarized light detection are realized,proving that the device meets the requirements of multi-function high-performance infrared photodetector application.Under 1550 nm incident light irradiation,the b P/n-Ge device has a high responsivity of 6.08 A/W under reverse bias conditions and a high detectivity of5.39×10¹¹ Jones due to the low dark current,the open circuit voltage could reach 0.34 V,the current polarization ratio to polarized light could reach 4.25,and the response speed could be lower than 10μs;2.Based on the thin thickness of two-dimensional materials and the characteristics of being easily modulated by electric fields,the influence of gate voltage modulation on the photoelectric properties of two-dimensional and three-dimensional heterojunctions is further studied,and a Mo S₂/Ge heterojunction modulated by the top gate is proposed.The contact of the device is optimized,and the mechanism of contact optimization on device performance is revealed.The ambipolar infrared light response is obtained,and the physical mechanism of ambipolar photocurrent is revealed.Finally,the wavelength-distinguishing photodetection is realized.The rectification ratio could be adjusted in the range of 0.09 to7.3 by adjusting the top gate voltage.Gr as the contact electrode of Mo S₂ could significantly improve the responsivity and response speed of the device to 1550 nm wavelength light.The responsivity of the device is adjustable from 33.7 A/W to–128 m A/W;3.Based on the ambipolar carrier transport characteristics of WSe₂,the top gate control structure is introduced into the junction field effect transistor（JFET）,and a mixed gate control WSe₂/Ge heterojunction transistor device is designed.Under the control of the top gate,the device could switch between n-type and p-type devices.The electrical characteristics of the device are studied,and the working mechanism of the device is analyzed.The optical characteristics of the device show that the hybrid gate controls the WSe₂/Ge heterojunction transistor.Wavelength-distinguishing photodetection is achieved,and due to the structural advantages of JFET,the device also achieves high-performance light detection.The n JFET and p JFET modes have low sub-threshold swings of 102 and 65m V/dec,respectively,and the current switching ratio reaches 10⁵.The photoelectric characteristics show that n JFET and p JFET have positive photocurrent under 532 nm and negative photocurrent under 1550 nm;4.Based on the characteristics of the precise control of the device by the multi-gate structure,a multi-gate modulated WSe₂/Mo S₂ heterojunction transistor is prepared,and the modulation effect of the back gate on the carrier transport characteristics of the WSe₂/Mo S₂heterojunction is analyzed,revealing the physical mechanism of negative differential transconductance,the rectification direction of the device could be reversed by back gate voltage,and the forward and reverse rectification ratios could reach 10⁴.The peak and valley voltages of the negative differential transconductance transfer curves vary with the carrier concentration in the Mo S₂ and WSe₂ channels,respectively,and the energy band model of the device under multi-gate modulation is established.Finally,based on the diversity of the device,variety of logic operations is realized.