Research On Nanoelectronic And Optoelectronic Devices Based On Two-dimensional Ferroelectric Negative Capacitance Effect

With the feature size of metal-oxide-semiconductor field-effect transistors（MOSFETs）approaching physical limits,power consumption has become the main bottleneck restricting the performance of integrated circuit chips.The power consumption of a semiconductor field effect transistor is closely related to the subthreshold swing of the device.Due to the carrier distribution restricted by Boltzmann’s law of thermodynamics,the traditional field-effect transistor’s subthreshold swing has a theoretical limit of 60 mV/dec.By introducing ferroelectric negative capacitance,semiconductor transistors can amplify the control effect of the gate voltage on the channel and overcome the limit of 60 mV/dec.Therefore,ferroelectric negative capacitance field effect transistors have become an important research direction for the development of low-voltage and low-power devices.Negative capacitance devices prepared by traditional ferroelectric materials still face severe challenges due to the influence of interface defects and critical size effects.The two-dimensional ferroelectric materials with non-dangling bond interface and atomic-level thickness characteristics provide an important solution for the development of novel high-performance negative capacitance transistors.In this regard,this paper takes the novel electronic and optoelectronic devices of low-dimensional ferroelectric materials as the research topic.Based on the advantage of 2D ferroelectric material CuInP₂S₆ with Curie temperature higher than room temperature,atomic-level thickness and high interface quality,the two-dimensional ferroelectric negative capacitance field effect transistor is constructed.And the electrical and photoelectric properties of the device are systematically studied.The main research contents are as below:（1）The photoelectric and ferroelectric properties of the two-dimensional ferroelectric material CuInP₂S₆ are studied.By testing the photoelectric response of CuInP₂S₆ under different wavelengths of light,it is determined that the limit wavelength of CuInP₂S₆response is less than 633 nm.The PFM results show that CuInP₂S₆ sample has good ferroelectric polarization characteristics.Additionally,the electrical properties of the CuInP₂S₆ diode under different voltage scanning ranges and different temperatures have been studied.The coercive field of the CuInP₂S₆ sample has been determined to be7.89*10⁴ V mm^-1.And the Curie temperature of the CuInP₂S₆ sample is around 320 K.These study of basic properties of CuInP₂S₆ provides fruitful information for the preparation of two-dimensional CuInP₂S₆ NC-FET.（2）The electrical properties of CuInP₂S₆/MoS₂ 2D-NC-FET are systematically studied.The influence of channel carrier concentration,CuInP₂S₆ thickness,CuInP₂S₆polarization and gate voltage scanning parameters on the electrical characteristics of the NC-FET are determined.A two-dimensional negative capacitance device with the sub-threshold swing as low as 24.9 mV/dec and the hysteresis of 430 mV is realized.Besides,the device performance is optimized from the points of interface engineering and capacitance matching.The interface engineering improves the stability of the NC-FET,so that the subthreshold swing of the device is evenly distributed around 50mV/dec.And the capacitance matching successfully reduce the hysteresis of the device to 132 mV.These study will provide an experimental basis for the practical application of 2D NC-FET in the future.（3）Based on the understanding of the characteristics and advantages of the negative capacitance device,the photoelectric properties of the Gr/CuInP₂S₆/MoS₂ 2D-NC-FET are studied.A two-dimensional negative-capacitance photodetector with detectivity of1.7*10⁶ cm Hz^1/2 W^-1,responsivity of 23.4 A W^-1,external quantum efficiency of5456%and photoelectric response time of 100 ms has been realized.Compared with the photodetector with MoS₂ transistor structure on Si O₂ substrate,the detectivity is increased by four orders of magnitude.And the photoelectric response time was reduced by one order of magnitude.The negative capacitance effect of the two-dimensional ferroelectric CuInP₂S₆ can improve the photoelectric performance of MoS₂ itself,which provides a new idea for the preparation of new photodetectors.