Photodetection in p –n junctions formed by electrolyte-gated transistors of two-dimensional crystals

Transition metal dichalcogenidemonolayers have attracted much attention due to their strong light absorption and excellent electronic properties. These advantages make this type of two-dimensional crystal a promising one for optoelectronic device applications. In the case ofphotoelectric conversion devices such as photodetectors and photovoltaic cells, p –njunctions are one of the most important devices. Here, we demonstrate photodetection with WSe2monolayer films. We prepare the electrolyte-gated ambipolartransistors and electrostatic p –njunctions are formed by the electrolyte-gating technique at 270  K. Thesep-n junctions are cooled down to fix the ion motion (andp-n junctions) and we observed the reasonablephotocurrentspectra without the external bias, indicating the formation ofp-n junctions. Very interestingly, two-terminal devices exhibit higher photoresponsivity than that of three-terminal ones, suggesting the formation of highly balanced anion and cation layers. The maximum photoresponsivity reaches 5  mA/W in resonance with the first excitonic peak. Our technique provides important evidence for optoelectronics in atomically thin crystals.

Source: Applied Physics Letters - November 16, 2016 Category: Physics Authors: Daichi Kozawa, Jiang Pu, Ryo Shimizu, Shota Kimura, Ming-Hui Chiu, Keiichiro Matsuki, Yoshifumi Wada, Tomo Sakanoue, Yoshihiro Iwasa, Lain-Jong Li and Taishi Takenobu Source Type: research