Ferroelectric Regulation Mechanism Of Charge Transfer And Its Application In Photodetectors

The combination of 2D semiconductor materials and ferroelectric materials is a unique heterogeneous structure,and the study of this heterogeneous structure can explore new physical phenomena.Ferroelectric materials with rich functions have long been considered as an excellent choice to expand the application range of 2D materials and improve the performance of devices.Especially in the research of photodetectors,the combination of 2D materials and ferroelectric materials makes ferroelectric gate photodetectors,which not only get rid of the higher gate voltage in traditional insulated gate photodetectors,but also change the doping density of semiconductor materials,modulate channel carriers and induce permanent interface heterostructure changes.Therefore,an in-depth study of the physical properties of ferroelectric-based heterostructures is increasingly important for the development of new integrated ferroelectric devices and the improvement of device performance.In this thesis,a ferroelectric gated photodetector with top-gate structure was prepared by physical vapor deposition and spin-coating,and a series of characterization tests were performed,which consisted of two main works:（1）P（VDF-TrEF）/SnS₂ ferroelectric gate photodetector:Compared with the traditional insulated gate transistor photodetector,the ferroelectric gate photodetector can effectively reduce power consumption,after polarization of the device,its ferroelectricity will make the P（VDF-TrEF）film residual polarization electric field,which makes the semiconductor surface charge density change,so that the effect of regulating the semiconductor doping density can be achieved,which is compared with the traditional use of voltage control channel carrier density The superiority is even more obvious when compared to the conventional use of voltage to control the channel carrier density.In this work,high quality SnS₂thin films and P（VDF-TrEF）thin films were grown to further prepare a low-power ferroelectric gate SnS₂photodetector.The photodetector has a stable switching response at 405nm laser,and the photodetector no longer requires additional gate voltage to modulate device performance after polarization.The dark current in the negative polarization state is reduced to3.32×10^-5times of the original one,and the switching ratio is changed from 0.4 to 6.4×10³in the unpolarized state.（2）Preparation and characterization of P（VDF-TrEF）/SnSe ferroelectric gate photodetector:As research on 2D materials continues to advance,it has been found that intrinsic carriers due to defects in semiconductor materials and surface charge enrichment due to surface oxidation,as well as high doping concentrations,can inhibit device performance during device preparation and testing.These inherent drawbacks lead to large dark currents,which reduce the ratio of photocurrent to dark current.In this thesis,SnSe films are also made into ferroelectric gate devices with top-gate structure.Compared with n-SnS₂films,the SnSe films prepared in this research work are p-type semiconductors,so they exhibit slightly different properties from n-type semiconductors.It is found that the P（VDF-TrEF）film can also reduce the dark current of the photodetector in the unpolarized state,and the polarization field in different directions has different effects on the device performance.The polarization electric field in different directions has different effects on the device performance.In the negatively polarized state,the photocurrent can be increased from 26.7n A to 270.8n A at the highest,which is about 10 times higher.