Ultrasensitive all-2D MoS ₂ phototransistors enabled by an out-of-plane MoS ₂ PN homojunction

Abstract

Two-dimensional transition metal dichalcogenide-based photodetectors have demonstrated potential for the next generation of 2-dimensional optoelectronics. However, to date, their sensitivity has not been superior to that of other technologies. Here we report an ultrasensitive two-dimensional photodetector employing an in-plane phototransistor with an out-of-plane vertical MoS ₂ p–n junction as a sensitizing scheme. The vertical built-in field is introduced for the first time in the transport channel of MoS ₂ phototransistors by facile chemical surface doping, which separates the photo-excited carriers efficiently and produces a photoconductive gain of >10 ⁵ electrons per photon, external quantum efficiency greater than 10%, responsivity of 7 × 10 ⁴ A W ⁻¹, and a time response on the order of tens of ms. This taken together with a very low noise power density yields a record sensitivity with specific detectivity \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D^*$$\end{document} of 3.5 × 10 ¹⁴ Jones in the visible and a broadband response up to 1000 nm.

Abstract

Photodetectors based on 2D transition metal dichalcogenides exhibit ever increasingly competitive performance, yet not superior to that of alternative technologies. Here, the authors devise a MoS ₂-based phototransistor with an out-of-plane junction, yielding a record detectivity combined with broadband response.