Theory of thermionic emission from a two-dimensional conductor and its application to a graphene-semiconductor Schottky junction

TL;DR

This paper develops a new theory for thermionic emission from two-dimensional conductors like graphene, accounting for out-of-plane charge motion due to finite quasiparticle lifetime, and applies it to graphene-semiconductor Schottky junctions.

Contribution

It introduces a fundamental theory for thermionic emission in 2D materials, differing from traditional 3D models, and derives a new thermionic constant for graphene-semiconductor interfaces.

Findings

The out-of-plane charge motion in 2D conductors arises from finite quasiparticle lifetime.

The thermionic constant depends on Schottky barrier height and Fermi level, not the Richardson constant.

The theory accurately describes thermionic emission in graphene-based Schottky junctions.

Abstract

The standard theory of thermionic emission developed for three-dimensional semiconductors does not apply to two-dimensional materials even for making qualitative predictions because of the vanishing out-of-plane quasiparticle velocity. This study reveals the fundamental origin of the out-of-plane charge carrier motion in a two-dimensional conductor due to the finite quasiparticle lifetime and huge uncertainty of the out-of-plane momentum. The theory is applied to a Schottky junction between graphene and a bulk semiconductor to derive a thermionic constant, which, in contrast to the conventional Richardson constant, is determined by the Schottky barrier height and Fermi level in graphene.