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.
@article{arxiv.1505.00282,
title = {Which is conducive to high responsivity in a hybrid graphene-quantum dot transistor: Bulk- or layer- heterojunction},
author = {Yating Zhang and Xiaoxian Song and Ran Wang and Haiyan Wang and Yongli Che and Xin Ding and Jianquan Yao},
journal= {arXiv preprint arXiv:1505.00282},
year = {2015}
}