# Abrupt p-n junction using ionic gating at zero-bias in bilayer graphene

## TL;DR

This paper demonstrates a novel method to create abrupt p-n junctions in bilayer graphene using ionic gating at zero bias, revealing enhanced photothermoelectric effects and potential for large-area optoelectronic devices.

## Contribution

The authors introduce a new technique combining electrostatic and electrolytic gating to form abrupt p-n junctions in bilayer graphene without bias, enabling improved optoelectronic properties.

## Key findings

- Presence of two Dirac peaks confirms p-n junction formation.
- Photovoltage increases at lower temperatures, indicating supercollision scattering.
- Six-fold photovoltage pattern suggests hot electron photothermoelectric effect.

## Abstract

Graphene is a promising candidate for optoelectronic applications. In this report, a double gated bilayer graphene FET has been made using a combination of electrostatic and electrolytic gating in order to form an abrupt p-n junction. The presence of two Dirac peaks in the gating curve of the fabricated device confirms the formation of a p-n junction. At low temperatures, when the electrolyte is frozen intentionally, the photovoltage exhibits a six-fold pattern indicative of the hot electron induced photothermoelectric effect that has also been seen in graphene p-n junctions made using metallic gates. We have observed that the photovoltage increases with decreasing temperature indicating a dominant role of supercollision scattering. Our technique can also be extended to other 2D materials and to finer features that will lead to p-n junctions which span a large area, like a superlattice, that can generate a larger photoresponse. Our work creating abrupt p-n junctions is distinct from previous works that use a source-drain bias voltage with a single ionic gate creating a spatially graded p-n junction.