Journal
ACS NANO
Volume 8, Issue 8, Pages 8653-8661Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn503521c
Keywords
photodetector; contact effect; Schottky barrier; tungsten diselenide; 2D material
Categories
Funding
- Academia Sinica, National Science Council Taiwan [NSC-102-2119-M-001-005-MY3]
- US AFOSR-BRI
- MOE AcRF Tier 1 grant [R-144-000-321-112]
- KAUST
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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 photo transistors 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 (10(5)) and specific detectivity (10(14)Jones), values higher than commercial Si- and InGaAs-based photodetectors; however, the response speed is longer than 5s 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.
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