Pinning-induced pn junction formation in low-bandgap two-dimensional semiconducting systems

TL;DR

This paper presents a model for $pn$ junction formation in 2D semiconductors like graphene, highlighting carrier switching, depletion regions, and their impact on device resistance near metal contacts.

Contribution

It introduces a novel model explaining $pn$ junction formation and parasitic resistance in 2D semiconducting systems near metal contacts.

Findings

Carrier type switching occurs near metal contacts.

Depletion regions depend on bias and affect device resistance.

The model is validated through transfer length structure experiments.

Abstract

A model is presented for $pn$ junction formation near metal-semiconductor contacts in two-dimensional semiconducting systems such as graphene. Carrier type switching occurs in a region near the metal-semiconductor junction when energy band bending leads to a crossing between the junction Fermi level and the Dirac energy. A bias-dependent depletion region occurs due to the minimization of carrier density, which is shown to act as an additional parasitic resistance in devices. The $pn$ junction resistance is demonstrated by its implementation in a transfer length structure.