Engineering Novel Transistors Based On Black Phosphorus

Abstract

Black phosphorus (BP), a layered 2D semiconductor that can be isolated to one monolayer thicknesses re-emerged in 2014 because of its promise for use in applications such as high performance MOSFETs, optoelectronic devices, novel devices like tunneling-field-effect-transistors (TFETs), and flexible electronics. The promise of BP comes from its unique material properties such as a high mobility, crystal anisotropy, a tunable direct band gap, an anisotropic effective mass, and the ability to scale to sub-1 nm thicknesses while retaining good electronic properties. These properties make BP particularly interesting as a possible post-silicon channel material in advanced logic transistors which could enable the continuation of transistor scaling beyond the foreseeable future. However, most experimental demonstrations of BP transistors have displayed poor OFF-state performance caused by gate-induced-drain-leakage (GIDL) which limits the device's overall usefulness. In this dissertation, novel BP transistors that utilize the unique properties of BP to improve OFF-state performance are demonstrated. These novel devices include a heterostructure BP MOSFET which utilizes the thickness-tunable band gap of BP to supress GIDL current, an electrostatically doped BP MOSFET which takes advantage the thin body of BP with a novel device structure used to effectively dope the source and drain regions of the BP, to again suppress GIDL current, and BP TFETs which utilize the anisotropic effective mass in order to open a path for realizing transistors with a subthreshold slope (SS) of less than 60 mV/dec in BP.