Role of Metal Contacts in High-Performance Phototransistors Based on WSe 2 Monolayers

Wenjing Zhang, Ming-Hui Chiu, Chang-Hsiao Chen, Wei Chen, Lain-Jong Li, Andrew Thye Shen Wee

Research output: Contribution to journalArticlepeer-review

290 Scopus citations

Abstract

Phototransistors based on monolayer transition metal dichalcogenides (TMD) have high photosensitivity due to their direct band gap transition. However, there is a lack of understanding of the effect of metal contacts on the performance of atomically thin TMD phototransistors. Here, we fabricate phototransistors based on large-area chemical vapor deposition (CVD) tungsten diselenide (WSe2) monolayers contacted with the metals of different work function values. We found that the low Schottky-contact WSe2 phototransistors exhibit a very high photo gain (105) and specific detectivity (1014Jones), values higher than commercial Si- and InGaAs-based photodetectors; however, the response speed is longer than 5 s in ambient air. In contrast, the high Schottky-contact phototransistors display a fast response time shorter than 23 ms, but the photo gain and specific detectivity decrease by several orders of magnitude. Moreover, the fast response speed of the high Schottky-contact devices is maintained for a few months in ambient air. This study demonstrates that the contact plays an important role in TMD phototransistors, and barrier height tuning is critical for optimizing the photoresponse and photoresponsivity. © 2014 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)8653-8661
Number of pages9
JournalACS Nano
Volume8
Issue number8
DOIs
StatePublished - Aug 12 2014

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