Скачать или смотреть Two-Dimensional Material-Based Negative-Capacitance Field-Effect Transistors... | Mayuri Sritharan

Abstract: Two-dimensional (2D) nanomaterials have presented a new avenue towards next-generation low power field-effect transistors (FETs) owed to their single-layer thickness and exceptional electronic/mechanical properties. Within the 2D material family, a certain subclass of 2materials in the transition metal dichalcogenide (TMD) family have recently generated great interest. These four MX2 materials, where M = zirconium or hafnium and X = sulfur or selenium, have been experimentally shown to form a natively compatible oxide layer with high dielectric constants. This well-matched, defect-free insulator layer with exceptional dielectric properties can help scale down the characteristic transistor size and supply voltage making them promising candidates for ultra-scaled low-power FET applications. However, since these 2D material-based FETs are still inhibited by the classical switching limit, this motivates the introduction of a ferroelectric (FE) layer. FE materials can exhibit hysteretic responses of spontaneous polarization to an applied electric field. Recent studies have demonstrated that FE materials can amplify the performance of FETs beyond the classical limit by using the polarization switching within the FE layer, a phenomenon known as negative capacitance (NC). As transistor feature sizes continue to scale down, novel NC-FET devices may be the key to realizing ultra-scaled and low-power devices and thus, motivates our research. Before simulating these NC-FET devices, the 2D material-based FET must first be optimized. Hence, we investigate zirconium and hafnium dichalcogenide based FETs using atomistic quantum transport simulations. Material properties are simulated using density functional theory (DFT). Transport is modelled by self-consistently solving the non-equilibrium Green's function (NEGF) and Poisson’s equation to compute the channel charge and potential. Through this research, we hope to develop a solid understanding behind the physics and performance of the four materials and isolate a single material that performs best at ultra-scaled channel lengths (sub-10 nm). From the optimized 2D material-based FET, we will then extend our investigation into 2D material-based NC-FET devices. The tools and methodology developed through our research will be paramount to researchers and engineers who wish to develop next generation energy-efficient electronics.