Journal
NANOSCALE
Volume 15, Issue 10, Pages 4940-4950Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d2nr06263a
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A lateral 2D WSe2 p-n homojunction with low contact resistance and high photoresponsivity was constructed using a plasma-treated doping method.
Conventional doping schemes of silicon (Si) microelectronics are incompatible with atomically thick two-dimensional (2D) transition metal dichalcogenides (TMDCs), which makes it challenging to construct high-quality 2D homogeneous p-n junctions. Herein, we adopt a simple yet effective plasma-treated doping method to seamlessly construct a lateral 2D WSe2 p-n homojunction. WSe2 with ambipolar transport properties was exposed to O-2 plasma to form WOx on the surface in a self-limiting process that induces hole doping in the underlying WSe(2)via electron transfer. Different electrical behaviors were observed between the as-exfoliated (ambipolar) region and the O-2 plasma-treated (p-doped) region under electrostatic modulation of the back-gate bias (V-BG), which produces a p-n in-plane homojunction. More importantly, a small contact resistance of 710 omega mu m with a p-doped region transistor mobility of similar to 157 cm(2) V-1 s(-1) was achieved due to the transformation of Schottky contact into Ohmic contact after plasma treatment. This effectively avoids Fermi-level pinning and significantly improves the performance of photodetectors. The resultant WSe2 p-n junction device thus exhibits a high photoresponsivity of similar to 7.1 x 10(4) mA W-1 and a superior external quantum efficiency of similar to 228%. Also, the physical mechanism of charge transfer in the WSe2 p-n homojunction was analyzed. Our proposed strategy offers a powerful route to realize low contact resistance and high photoresponsivity in 2D TMDC-based optoelectronic devices, paving the way for next-generation atomic-thickness optoelectronics.
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