Photoinduced Tuning of Schottky Barrier Height in Graphene/MoS₂ Heterojunction for Ultrahigh Performance Short Channel Phototransistor

Abstract

Two-dimensional (2D) layered materials with properties such as a large surface-to-volume ratio, strong light interaction, and transparency are expected to be used in future optoelectronic applications. Many studies have focused on ways to increase absorption of 2D-layered materials for use in photodetectors. In this work, we demonstrate another strategy for improving photodetector performance using a graphene/MoS₂ heterojunction phototransistor with a short channel length and a tunable Schottky barrier. The channel length of sub-30 nm, shorter than the diffusion length, decreases carrier recombination and carrier transit time in the channel and improves phototransistor performance. Furthermore, our graphene/MoS₂ heterojunction phototransistor employed a tunable Schottky barrier that is only controlled by light and gate bias. It maintains a low dark current and an increased photocurrent. As a result, our graphene/MoS₂ heterojunction phototransistor showed ultrahigh responsivity and detectivity of 2.2 × 10⁵ A/W and 3.5 × 10¹³ Jones, respectively. This is a considerable improvement compared to previous pristine MoS₂ phototransistors. We confirmed an effective method to develop phototransistors based on 2D materials and obtained ultrahigh performance of our phototransistor, which is promising for high-performance optoelectronic applications.