Design of Au urchin embedded in PMMA: A solution to balance photoresponse and dark-current for WS2 plasmonic photodetectors

The local surface plasmon resonance effect has made an outstanding contribution to high-performance optoelectronic devices due to its unique light absorption ability. However, it is urgent to solve the accompanying problem of high dark-current, which is mainly caused by interface damage and charge transfer between plasma structure and material. In this work, we designed a plasma structure of Au urchin embedded in the PMMA layer to effectively balance photo-response and dark-current for WS2 plasmonic photodetectors (PDs). Herein, the non-contact “metal–semiconductor” integration prevents free electron injection and avoids the carrier lifetime extension caused by interfacial defect, which guarantees low dark-current and high carrier mobility of WS2. In particular, compared to conventional spherical metal nanoparticles, the multi-tip Au urchin allows better light absorption enhancement and accelerated carrier separation, as confirmed by finite-difference time-domain simulations. As a result, the WS2/PMMA@Au urchin plasmonic PD achieves 3.6-fold reduction in dark-current, thus obtaining a high responsivity of 533 A/W, a detectivity of 1.46 × 1010 Jones, and an ultra-fast response speed of 136 ns. Our proposed plasma structure provides a way for promoting weak-light detection and high-efficiency photoelectric conversion of low-dimensional optoelectronic devices.