Two-Dimensional Black Phosphorus for High Performance Field Effect Transistors

Abstract

Two-dimensional (2D) materials are a potential platform for scaled logic devices, sensor applications, flexible electronics and other innovative device concepts. Black phosphorus (BP) has recently emerged as a new promising layered semiconductor due to its unique material properties. BP has high electron and hole mobility, tunable band-gap ranging from 0.3 eV (bulk) to 1-2 eV (monolayer) and highly asymmetric effective mass. BP metal-oxide-semiconductor field-effect transistors (MOSFETs) have the potential to outperform other 2D semiconductors mainly due to the lighter effective mass of BP, which leads to higher mobility, and narrower band gap, which can reduce contact resistance due to the Schottky barrier height lowering. In this dissertation, BP n- and p-type MOSFETs with record performance are demonstrated. A comprehensive experimental and theoretical evaluation of the design and operating parameters that limit the off-state performance and subthreshold slope in BP MOSFETs is performed. Next, for the first time, the effect of asymmetric crystal orientation on BP MOSFET performance is quantified and the anisotropic mobility in a realistic MOSFET geometry is analyzed. Finally, contact engineering is utilized to achieve record-low contact resistance in BP p-MOSFETs.