Impact of Dimensionality on PN Junctions

TL;DR

This paper investigates how reducing dimensionality in PN junctions from 3D to 1D significantly alters their electrostatic properties, with analytical models matching experiments and simulations, revealing new sensitivities for sensor applications.

Contribution

It introduces novel analytical equations for 2D and 1D PN junctions that incorporate neutral regions, highlighting the impact of dimensionality on electrostatics.

Findings

Decreased dimensionality increases fringing fields and depletion width.

Depletion width dependence shifts from square root in 3D to linear and exponential in 2D and 1D.

1D PN junctions show heightened sensitivity to control parameters, useful for sensors.

Abstract

Low dimensional material systems provide a unique set of properties useful for solid-state devices. The building block of these devices is the PN junction. In this work, we present a dramatic difference in the electrostatics of PN junctions in lower dimensional systems, as against the well understood three dimensional systems. Reducing the dimensionality increases the fringing fields and depletion width significantly. We propose a novel method to derive analytic equations in 2D and 1D that considers the impact of neutral regions. The analytical results show an excellent match with both the experimental measurements and numerical simulations. The square root dependence of the depletion width on the ratio of dielectric constant and doping in 3D changes to a linear and exponential dependence for 2D and 1D respectively. This higher sensitivity of 1D PN junctions to its control parameters can be used towards new sensors.