Research On The Mechanism And Device Fabrication Of Improved Photodetection Of Two-Dimensional Semiconductor

Two-dimensional(2D)semiconductors have become a research hotspot in recent years due to their unique structure and excellent physical properties.These 2D semiconductors include 2D layered materials,2D perovskites,and 2D nanosheets.Their band gaps cover the spectrum from visible light to infrared,showing huge application prospects in the field of new photoelectric detection.How to make full use of the photoelectric conversion mechanism and give full play to the advantages of 2D semiconductors in terms of device performance and function has always been a research area that researchers focus on.So far,2D semiconductor-based photodetectors have been widely reported,but they need to be greatly improved before they can be put into practical use.For example,2D layered materials have low light absorption efficiency due to their thickness reduction to atomic level;Some 2D materials are susceptible to the influence of the environment,leading to unstable photoelectric performance;2D transition metal sulfide photoelectric field-effect transistor(FET)devices have low optical switching ratio,high dark current,and slow response speed and so on.This dissertation takes solving these problems as the starting point and carries out theoretical research work to enhance the 2D semiconductor photodetection,with the purpose of preparing a 2D material photodetector with excellent performance.The main research contents and results are as follows:1.The high-gain photodetector of MoS₂ enhanced by CdSe quantum dots has been studied.Using CdSe colloidal quantum dots as the top floating gate of FET,under the photogating effect,the floating gate can control the carrier concentration of the MoS₂ channel,which greatly increases the photocurrent of the device when illuminated,obtaining a very high gain.The results show that the photocurrent of the device with the addition of the quantum dots photosensitive layer is three orders of magnitude higher than that of the original MoS₂ phototransistor,and the responsivity is increased by 4400 times.Then we studied the physical mechanism of the quantum dot enhanced MoS₂ photodetector,and the charge transfer and non-radiative energy resonance transfer process between the quantum dot and MoS₂ are discussed.Finally,the relationship between the gain effect of quantum dots on the MoS₂ photodetector and the thickness of MoS₂ was further studied,and we found that as the thickness of MoS₂ increased,the gain effect of quantum dots decreased.2.The photoelectric properties of the 2D InSb nanosheet photodetector were studied,and the device was passivated by the ferroelectric polymer film P(VDF-TrFE),and the highly sensitive 2D InSb nanosheet photodetector was obtained under the control of the ferroelectric local electric field.The results show that the P(VDF-TrFE)thin films can not only passivate the surface of 2D InSb nanosheets but also can adjust the performance of 2D InSb nanosheet photodetectors through the ferroelectric local field with upward polarization,so the device can work on a very low dark current level under zero gate voltage,which improves the sensitivity of the device.The 2D InSb nanosheet photodetector shows a clear light response for visible light to mid-infrared,with a responsivity of 14.9 A W^-1 at 4.3?m.The 2D InSb photodetector is passivated by the ferroelectric thin film,and the P(VDF-TrFE)is polarized upward by an external gate voltage.The current of the device is strongly suppressed to 3 nA,and the wavelength responsivity reaches 311.5 AW^-1 at 940 nm,the detectivity is 9.8×10⁹ Jones,and the response time is only 2 ms.In summary,this paper studies the application of 2D materials represented by transition metal sulfide MoS₂ and traditional mid-infrared material InSb nanosheets in the field of photoelectric detection reveals the new mechanism of photoelectric enhancement of 2D materials,and finally completes the fabrication of the devices and performance test characterization.The research work and results of this paper have important guiding significance for promoting the practical application of 2D semiconductor photodetectors.