Sensitive photodetection is crucial for modern optoelectronic technology. Two-dimensional molybdenum disulfide (MoS2) with unique crystal structure, and extraordinary electrical and optical properties is a promising candidate for ultrasensitive photodetection. Previously reported methods to improve the performance of MoS2 photodetectors have focused on complex hybrid systems in which leakage paths and dark currents inevitably increase, thereby reducing the photodetectivity. Here, we report an ultrasensitive negative capacitance (NC) MoS2 phototransistor with a layer of ferroelectric hafnium zirconium oxide film in the gate dielectric stack. The prototype photodetectors demonstrate a hysteresis-free ultra-steep subthreshold slope of 17.64 mV/dec and ultrahigh photodetectivity of 4.75 × 1014 cm Hz1/2 W−1 at room temperature. The enhanced performance benefits from the combined action of the strong photogating effect induced by ferroelectric local electrostatic field and the voltage amplification based on ferroelectric NC effect. These results address the key challenges for MoS2 photodetectors and offer inspiration for the development of other optoelectronic devices.

Conventional field-effect transistors (FETs) are not expected to satisfy the requirements of future large integrated nanoelectronic circuits because of these circuits' ultra-high power dissipation and because the conventional FETs cannot overcome the subthreshold swing (SS) limit of 60 mV/decade. In this work, the ordinary oxide of the FET is replaced only by a ferroelectric (Fe) polymer, poly(vinylidene difluoride-trifluoroethylene) (P(VDF-TrFE)). Additionally, we employ a two-dimensional (2D) semiconductor, such as MoS 2 and MoSe 2 , as the channel. This 2D Fe-FET achieves an ultralow SS of 24.2 mV/dec over four orders of magnitude in drain current at room temperature; this sub-60 mV/dec switching is derived from the Fe negative capacitance (NC) effect during the polarization of ferroelectric domain switching. Such 2D NC-FETs, realized by integrating of 2D semiconductors and organic ferroelectrics, provide a new approach to satisfy the requirements of next-generation low-energy-consumption integrated nanoelectronic circuits as well as the requirements of future flexible electronics.

such as steep subthreshold swing (SS), high switching ratio (I on /I off ), adjustable hysteresis, compatibility with standard semiconductor fabrication processes, and environmental friendliness, promotes NCFET to be a promising candidate to lower power consumption and solve the heat problem in ULSI.As early as the 1960s, the concept of negative capacitance (NC) was proposed in amorphous semiconductor chalcogenides thin film, [25,26] then the NC effect was observed in several devices, such as p-n junctions, [27,28] Schottky diodes, [29,30] metal-insulator-metal diodes, [31] and others. [32][33][34][35] Concretely, the NC effect occurs when the reciprocal of the second derivation of potential energy U with respect to the ferroelectric polarization charge Q F is negative, which is usually achieved during the switching process of ferroelectric polarization. [36,37] NCFET achieves steep SS through the NC voltage amplification effect by adding a ferroelectric layer into the transistor gate stack. [22] NCFET simulation methods vary according to the types of transistor gate structures-metal ferroelectric semiconductor field-effect transistor (MFSFET), metal ferroelectric insulator semiconductor field-effect transistor (MFISFET), and metal ferroelectric metal insulator semiconductor field-effect transistor (MFMISFET). However, the basic principle is to realize a match between the channel charge Q and the ferroelectric polarization charge P, [38][39][40][41][42] no matter what the specific gate structure is.Furthermore, the influencing factors of NCFET's electrical properties have been qualitatively analyzed and summarized according to numerous simulation results. Commonly, a tradeoff exists between SS and hysteresis, [22] and we can design and manipulate the gate structure, [41] ferroelectric thickness (t Fe ), [22] ferroelectric material parameters, [38] silicon doping concentration, [39,43] temperature, [44] work frequency, [45][46][47][48] and high-κ dielectric [23,49,50] to optimize the electrical performance of NCFET and meet specific practical application requirement.The experimental researches on NCFETs can be mainly classified into three categories based on various kinds of ferroelectrics. First, the NCFET based on organic ferroelectric-poly(vinylidene difluoride-trifluoroethylene)[P(VDF-TrFE)], has been experimentally demonstrated, and achieves minimum SS (SS min ) = 13 mV dec −1 with small hysteresis. [51,52] Second, the NCFET based on lead zirconate titanate (PZT), a type of inorganic perovskite-type ferroelectric, exhibits hysteretic switching with With the progress in silicon circuit miniaturization, lowering power consumption becomes the major objective. Supply voltage scaling in ultralargescale integration (ULSI) is limited by the physical barrier termed "Boltzmann Tyranny." Moreover, considerable heat is inevitably generated from the ultrahighly integrated circuit. To solve these problems, a ferroelectric negative capacitance field-effect transistor (Fe-NCFET) is proposed in order to reduce the subthresho...