Role of Metal Contacts in High-Performance Phototransistors Based on WSe2 Monolayers
Role of Metal Contacts in High-Performance Phototransistors Based on WSe2 Monolayers
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DOI：
10.1021/nn503521c
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发表时间：
2014-08-01
期刊：
影响因子：
17.1
通讯作者：
Wee, Andrew Thye Shen
中科院分区：
文献类型：
--
作者：
Zhang, Wenjing;Chiu, Ming-Hui;Wee, Andrew Thye Shen
基于单层过渡金属二卤化物(TMD)的光敏晶体管由于其直接带隙跃迁而具有很高的光敏性。然而，对于金属接触对原子薄TMD光电晶体管性能的影响，人们缺乏了解。在这里，我们基于大面积化学气相沉积(CVD)二硒化钨(WSe2)单分子膜与不同功函数值的金属接触来制备光电晶体管。我们发现，低肖特基接触的WSe2光电晶体管表现出很高的光增益(10(5))和比探测率(10(14)琼斯)，高于商用的Si和InGaAs基光电探测器；然而，在环境空气中，响应速度超过5s。相比之下，高肖特基接触光电晶体管的快速响应时间小于23ms，但光增益和比探测率下降了几个数量级。此外，高肖特基接触器件的快速响应速度在环境空气中保持了几个月。这项研究表明，接触在TMD光电晶体管中起着重要的作用，势垒高度的调节是优化光响应和光响应度的关键。
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.