| Photodetector is such a device that converts an optical signal into an electrical signal.High-performance photodetectors play an important role in many areas of daily life,including photoelectric display,medical imaging,environmental monitoring,optical communications,military,security inspection and so on.Two-dimensional semiconductor materials have the right size band gap and no suspension bond surface,and still maintain stable photoelectric properties under the thickness of atomic level,becoming one of the competitive photoelectric materials today.However,common two-dimensional semiconductor photoconductive photodetectors have problems such as large dark current,low detection rate and slow response time.In order to effectively solve the above problems,metal-two-dimensional semiconductor Schottky barrier or p-n heterojunction structure can be used to construct photodetectors to generate built-in potential to reduce the dark current of devices and accelerate the separation of photogenerated electron-hole pairs,so as to further improve the performance of photodetectors.In this paper,based on the above principles,using van der Waals heterogeneous integration technology,two-dimensional semiconductor molybdenum disulfide（Mo S2）Schottky photodetector and two-dimensional semiconductor Mo S2/black phosphorus（BP）heterojunction photo memory based on thermal electron emission model are developed.The specific research content of this paper is as follows:（1）Based on the high work-function difference between two-dimensional semiconductor Mo S2 and metal electrode,a vertical photodetector with Schottky contact of Au-Mo S2 is developed by using van der Waals heterogeneous integration technology.The perfect van der Waals heterointerface between Mo S2 and Au electrode with high work-function can be constructed by using van der Waals heterogeneous integration technology,which effectively avoids Fermi level pinning effect.Therefore,a large Schottky barrier height（）is formed between Mo S2 and Au electrode,which makes the device have Schottky rectification characteristics and reduces the dark current of the device.Under the light intensity density of0.134m W/mm-2（VR=-2 V）,the light/dark current ratio of the device is 102 and the responsivity is 1.5 A/W.Due to the nanoscale conductive channel formed by the vertical structure of Au-Mo S2-Ag,the photodetector greatly reduces the response time of optical detection.In addition,based on the thermal electron emission model,four cases in which the responsivity varies with intensity density and applied bias are analyzed in detail,which provides guidelines for comparing the responsivity and other performance indexes of two-dimensional semiconductor photodetectors.（2）Based on the photoelectric characteristics of two-dimensional semiconductor Mo S2and BP,the Mo S2/BP heterojunction photoelectric memory is prepared by using van der Waals heterogeneous integration technology.The auto-oxidation of BP is used to generate charge traps and capture photo-generated charge carriers,which avoids the complicated process of introducing metal impurities into the device or inserting oxide layer.The photoelectric memory can write and erase easily by adjusting the grid voltage Vg of the device and incident laser pulse,and has a fast write and erase speed,with a write erase ratio of 103.The device exhibits a unique"N"shaped transfer curve and can be used as a photodetector at specific grid voltages,showing excellent detection performance with detectivity up to 1014 Jones.In addition,the photoelectric memory can be trained by the neural network for image recognition,recognition rate of up to 91%,also can use the p-n junction rectification characteristics to realize the dynamic sine wave rectification,which shows that the device can be applied to the primary logic circuit. |
