The Study Of High Gain Photodetector Based On Low Dimensional Materials

In the past decade,nanomaterial photodetectors have been extensively studied,mainly focusing on various novel low-dimensional materials,such as one-dimensional materials and two-dimensional materials.Low-dimensional materials have at least one dimension in three-dimensional space comparable to the mean free path of electrons,so they exhibit some novel physicochemical properties,such as quantum confinement effect,ballistic transport,intrinsic anisotropy,etc.,which is improving a new approach to achieve high sensitivity,wide spectrum,high speed response and polarized imaging.Infrared polarization detection can effectively identify the detected target from complex background radiation,so it has broad application prospects in tumor medical,geological exploration and meteorological monitoring.Especially in the field of quantum communication,infrared polarized photon detection is of great significance.This thesis mainly focuses the practical application of high-gain photodetectors based on low-dimensional materials in the field of single-photon detection.The main contents are as follows:1.Photodetectors based on WS₂ and MoS₂ floating gate structures have been studied.The gold nanoparticles of 1 nm thickness are used as a floating gate electron-trapping layer,floating upon the channel material WS₂.Under the control of the top gate ITO transparent electrode,free electrons are tunneled back and forth between the floating gate and the channel WS₂.The device exhibits a long"program"state and an"erase"state,and using a very low dark current(10^-11 A)under the programmed state for light responsing results the responsivity of 1090 A/W and detectivity of 3.5 x 10¹¹ Jones.In addition,the MoS₂ floating-gate photodetector in the same structure was fabricated,which also proved to have extremely strong light detection capability.2.A room temperature single-photon detector based on one-dimensional nanowires was studied.Based on the photogating gain mechanism,a core-shell CdS nanowire field-effect transistor was constructed.Single photon was successfully detected at room temperature and the detector can resolve 1³ photons.The detection efficiency is 23%and the dark count rate is 1.87×10^-3 Hz.In addition,benifting from the one-dimensional structure of nanowires,the device exhibits selective absorption characteristics of polarized photons.Meanwhile,an electrostatic field amplification model was established,showing that the theoretical values are in good agreement with the experimental values.3.Combinating of photogating effect concept and rectification characteristics,an asymmetric?electrode and area?InP nanowire field-effect transistor was designed and fabricated.The device has a rectification ratio of 10⁶@±6 V at room temperature and10⁸@at±5 V at 77 K.In addition,after the nanowire was completely depleted by surface state,where 6 photons/s is detected.4.According to the energy band engineering concept,a stacking structure of black phosphorus?BP?vertical WSe₂ was designed and studied.Due to the different band gaps between BP and WSe₂,the device exhibits dual-band detection capability.The built-in electric field quickly and efficiently separates the photo-generated carriers.BP acts as a photogating layer to provide huge gain.The responsbilities in the visible and infrared ranges are as high as 10³ A/W and 0.5 A/W,respectively,and the detectivities are as high as 10¹⁴ and 10¹00 Jones,respectively and the response speeds are 800?s.In addition,due to the intrinsic polarization sensitivity of BP,the device exhibits polarization selectivity for wavelength at 1550 nm.