Explicit gain equations for hybrid graphene-quantum-dot photodetectors

TL;DR

This paper derives explicit gain equations for hybrid graphene-quantum-dot photodetectors, explaining high photo gain through surface depletion and photovoltage effects, supported by experimental data.

Contribution

It provides the first explicit gain equations for hybrid graphene-quantum-dot photodetectors, linking theoretical models with experimental results.

Findings

Explicit gain equations fit well with experimental data

High photo gain explained by surface depletion and photovoltage

Physical parameters extracted from the model

Abstract

Graphene is an attractive material for broadband photodetection but suffers from weak light absorption. Coating graphene with quantum dots can significantly enhance light absorption and create extraordinarily high photo gain. This high gain is often explained by the classical gain theory which is unfortunately an implicit function and may even be questionable. In this work, we managed to derive explicit gain equations for hybrid graphene-quantum-dot photodetectors. Due to the work function mismatch, lead sulfide (PbS) quantum dots coated on graphene will form a surface depletion region near the interface of quantum dots and graphene. Light illumination narrows down the surface depletion region, creating a photovoltage that gates the graphene. As a result, high photo gain in graphene is observed. The explicit gain equations are derived from the theoretical gate transfer characteristics of graphene and the correlation of the photovoltage with the light illumination intensity. The derived explicit gain equations fit well with the experimental data, from which physical parameters are extracted.