Gate Tunable Lateral 2D pn Junctions: An Analytical Study of Its Electrostatics

TL;DR

This paper develops analytical models for the electrostatics of gate-tunable 2D lateral pn junctions with electrostatic doping, validated by numerical simulations, highlighting differences from chemically doped devices.

Contribution

It provides the first analytical expressions for electrostatic potential and depletion width in electrostatically doped 2D pn junctions, independent of dielectric constant.

Findings

Depletion width depends on electrostatic potential and oxide thickness, not dielectric constant.

Models accurately match numerical simulations of MoS2-based junctions.

Analytical solutions apply to both symmetrical and asymmetrical gate configurations.

Abstract

The electrostatics of two-dimensional (2D) lateral pn homojunctions considering the impact of electrostatic doping by means of two split bottom-gates are studied here. Analytical expressions are obtained from the solution of the 2D Poisson equation considering a depletion approximation. Straightforward analytical models for the electrostatic potential and the depletion width within both the dielectric and the 2D semiconductor are obtained for both the symmetrical and asymmetrical cases. In contrast to the case of devices with chemical doping, the obtained depletion width model of devices with electrostatic doping do not depend on the dielectric constant but only on the electrostatic potential and oxide thickness. The models describe the electrostatics of gate-tunable 2D pn junctions at arbitrary bias. A benchmark against numerical device simulations of MoS2-based pn junctions validate the analytical models.