Impact of Thickness on Contact Issues for Pinning Effect in Black Phosphorus Field‐Effect Transistors

Metal/semiconductor contact is a significant constraint in short‐channel field effect transistors (FETs) comprising black phosphorus (BP) and other 2D semiconductors. Due to the pinning effect at metal/2D semiconductor interface, the Schottky barrier usually does not follow the Schottky–Mott rule, resulting in thickness‐dependent FET performance. In this work, the Schottky barrier in BP FETs is investigated via theory calculation and electrical measurement. A simple metal/BP contact model is presented based upon thickness‐dependent electrical characteristics of BP FETs. The model considers the Schottky barrier as a combined effect of the Schottky–Mott rule and the pinning effect and provides a feasibility to track the conducting behavior of other 2D semiconductor FETs. Metal/semiconductor contact is important for 2D materials field‐effect transistors (FETs). By theory simulation and experiments, the thickness‐dependent Schottky barrier is a combined effect of the Schottky–Mott rule and the pinning effect, and the contact can be improved by black phosphorus (BP) thickness. This provides a feasibility to track the thickness‐dependent conducting behavior of BP FETs and a direction to improve metal/semiconductor contact.