Dynamic Wavelength-Tunable Photodetector Using Subwavelength Graphene Field-Effect Transistors

TL;DR

This paper demonstrates that graphene field-effect transistors can achieve dynamic wavelength tunability through gate voltage modulation, revealing complex physical phenomena that enable this capability experimentally for the first time.

Contribution

It provides a detailed quantum transport model showing how gate voltage controls wavelength tunability in graphene photodetectors, highlighting the role of electromagnetic focusing and non-vertical transitions.

Findings

Wavelength tunability is achievable by dynamically changing the gate voltage.

Electromagnetic field focusing at contact edges enhances optical transitions.

Gate-dependent modulation of photocurrent is influenced by the Dirac point's density of states.

Abstract

Dynamic wavelength tunability has long been the holy grail of photodetector technology. Because of its atomic thickness and unique properties, graphene opens up new paradigms to realize this concept, but so far this has been elusive experimentally. Here we employ detailed quantum transport modeling of photocurrent in graphene field-effect transistors (including realistic electromagnetic fields) to show that wavelength tunability is possible by dynamically changing the gate voltage. We reveal the phenomena that govern the behavior of this type of device and show significant departure from the simple expectations based on vertical transitions. We find strong focusing of the electromagnetic fields at the contact edges over the same length scale as the band-bending. Both of these spatially-varying potentials lead to an enhancement of non-vertical optical transitions, which dominate even the absence of phonon or impurity scattering. We also show that the vanishing density of states near the Dirac point leads to contact blocking and a gate-dependent modulation of the photocurrent.