Tunable spontaneous emission from layered graphene/dielectric tunnel junctions

TL;DR

This paper introduces a theoretical concept for tunable light emission and optical gain from layered graphene/dielectric tunnel junctions, challenging the belief that graphene cannot spontaneously emit light, and demonstrates voltage-controlled emission spectra.

Contribution

It presents a novel theoretical framework for light emission and optical gain in graphene/dielectric tunnel junctions, with detailed quantum mechanical analysis and tunability via applied voltage.

Findings

Optical gain and emission spectra are tunable by voltage.

Quantum mechanical calculations confirm the feasibility of light emission.

Exact analysis of field-assisted tunneling supports the concept.

Abstract

There has been a rapidly growing interest in optoelectronic properties of graphene and associated structures. Despite the general belief on absence of spontaneous emission in graphene, which is normally attributed to its unique ultrafast carrier momentum relaxation mechanisms, there exist a few recent evidences of strong optical gain and spontaneous light emission from mono-layer graphene, supported by observations of dominant role of out-of-plane excitons in polycyclic aromatic hydrocarbons. In this article, we develop a novel concept of light emission and optical gain from simple vertical graphene/dielectric tunnel junctions. It is theoretically shown that the possible optical gain or emission spectrum will be easily tunable by the applied voltage. We present details of quantum mechanical calculations and perform an exact analysis of field-assisted tunneling using transfer matrices combined with expansion on Airy's functions.