Hao Xu

University of Electronic Science and Technology, China

Title: High-EQE near-infrared phototransistors based on ternary MoS2(1-x)Se2x nanoflakes

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Biography

Prof. Dr. Hao Xu is now a full-time Professor at University of Electronic Science and Technology of China (UESTC). He received his master degree in Microelectronics from Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, and achieved his Ph.D. degree in Photonics and Nanotechnology from University College London (UCL). His current research is focused on low-dimensional semiconductor physics and optoelectronic devices.

Abstract

Atomically thin transition metal dichalcogenides (TMDs) is a representative group in the 2D material family. Benefitted from tunable bandgap, good stability, unique optoelectronic properties, and reduced manufacturing process compared to group III-V semiconductors, they are a promising candidate for next-generation photonic and optoelectronic applications.  In the past decade, alloying engineering has been widely investigated to boost performance of binary TMD-based photodetectors, such as photoresponsivity and quantum efficiency. Here, we report a high-performance MoS2(1-x)Se2x  alloy phototransistor, delivering outstanding photoresponsivity, specific detectivity and EQE. The CVD-grown MoS2(1-x)Se2x  nanoflake shows a localized vertically-stacking homojunction region with composition and thickness gradient, which further induces localized bandgap gradient and internal electric field.  It is worth noting that the pyramid-shaped thickness variation only occurs in a triangular region with a 3 µm side, leaving the other parts of the entire flake (triangular with a side over 30 µm) uniform. It also shows an irregular distribution deviated from the center of the flake. The fabricated device exhibits photoresponsivity up to ~104 A/W, specific detectivity up to ~1014 Jones, and EQE of ~106 % under visible light illumination. When excited by near-infrared light, the phototransistor delivers an EQE of ~103%. These results provide brand-new thoughts for investigating the spatially graded properties of TMD alloy and the approach to enhance the performance of photodetectors.