Which is conducive to high responsivity in a hybrid graphene-quantum dot transistor: Bulk- or layer- heterojunction

TL;DR

This study compares layer- and bulk-heterojunction graphene-quantum dot transistors, finding that layer-heterojunctions offer higher responsivity and are better suited for near-infrared photodetection despite lower mobility.

Contribution

The paper provides a comparative analysis of heterojunction types in graphene-quantum dot transistors, highlighting the superior responsivity of layer-heterojunction structures for NIR detection.

Findings

Layer-heterojunction transistors have higher responsivity (106 A/W).

Mobility is higher in layer-heterojunction (677 cm2V-1s-1) than in bulk-heterojunction (314 cm2V-1s-1).

Transport mechanisms limit performance in bulk-heterojunction devices.

Abstract

Heterojunction, a photoelectric conversion center, plays a critical role in photo detection. A compare study is performed on field effect phototransistors (FEpT) with two typical heterojunctions based on graphene and PbSe quantum dots (QDs) hybrid, including layer-heterojunction (LH) and bulk-heterojunction (BH). LH-FEpT exhibits a higher mobility ({\mu}n) 677 cm2V-1s-1, whereas {\mu}n of BH-FEpT is as low as 314 cm2V-1s-1, however the higher responsivity (106 A/W) is achieved by the former. Because R is proportional to the product of mobility and transfer rate, and high transfer rate of LH-FEpT overcompensates the shortage of low mobility. Although large area of heterojunction and high mobility benefit high density of photo-induced carriers, lack of transport mechanism becomes to the main constrain factor in BH-FEpT. Therefore, LH-FEpT is a better candidate of near infrared (NIR) photo detectors.