High-Performance WSe 2 Phototransistors with 2D/2D Ohmic Contacts

• Published in: Nano letters Vol. 18; no. 5; pp. 2766 - 2771
• Main Authors: Wang, Tianjiao, Andrews, Kraig, Bowman, Arthur, Hong, Tu, Koehler, Michael, Yan, Jiaqiang, Mandrus, David, Zhou, Zhixian, Xu, Ya-Qiong
• Format: Journal Article
• Language: English
• Published: United States 09.05.2018
• Subjects: WSe2; ohmic contacts; Photocurrent; photodetector; TMDs
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.7b04205

We report high-performance WSe phototransistors with two-dimensional (2D) contacts formed between degenerately p-doped WSe and undoped WSe channel. A photoresponsivity of ∼600 mA/W with a high external quantum efficiency up to 100% and a fast response time (both rise and decay times) shorter than 8 μs have been achieved concurrently. More importantly, our WSe phototransistor exhibits a high specific detectivity (∼10 Jones) in vacuum, comparable or higher than commercial Si- and InGaAs-based photodetectors. Further studies have shown that the high photoresponsivity and short response time of our WSe phototransistor are mainly attributed to the lack of Schottky-barriers between degenerately p-doped WSe source/drain contacts and undoped WSe channel, which can reduce the RC time constant and carrier transit time of a photodetector. Our experimental results provide an accessible strategy to achieve high-performance WSe phototransistor architectures by improving their electrical transport and photocurrent generation simultaneously, opening up new avenues for engineering future 2D optoelectronic devices.