(Invited) From Field-Effect Transistors to Tunneling Devices and Resistive Random Access Memories in Two-Dimensional Van Der Waals Structures

Abstract

Devices from low-dimensional materials are fundamentally different from those in the conventional electronic world. The ultra-thin body of transition metal dichalcogenides (TMDs) and black phosphorus (BP) as examples of semiconducting layered structures enables electrostatics gate control that goes beyond what can be achieved by even the most aggressively scaled three-dimensional silicon FinFET technology. Moreover, the arrangement of bonds in a two-dimensional system defines a natural sub-nanometer channel thickness without loss of carrier mobility as would be typically observed when thinning down a three-dimensional semiconductor to similar dimensions. At the same time the anisotropic transport conditions in layered two-dimensional (2D) systems allow for novel device applications. In my talk, I will present three device implementations that take explicitly advantage of the unique properties of two-dimensional van der Walls (vdW) materials. First, I will discuss a multi-layer channel device from MoS2 that exploits the advantage of stacking 2D vdW materials in a three-dimensional (3D) integration approach. I will show how multi-channel TMD field-effect transistors (FETs) are fabricated, will discuss the associated challenges and finally present the experimental transport results. Next, tunneling field-effect transistors (TFETs) from black phosphorus (BP) will be presented that show record high tunneling current densities and good inverse subthreshold slopes in a reconfigurable device geometry. Last, I will present experimental and simulation results on the topic of resistive random access memories (RRAM) from multi-layer MoTe2 and Mo1-xWxTe2. Excellent switching characteristics of these novel types of two-terminal devices are presented in conjunction with a model to explain the observed switching behavior in terms of an electric field induced structural transition from a 2H semiconducting to a distorted transient structure (2Hd) and orthorhombic Td conducting phase.