Layered-material WS2/topological insulator Bi2Te3 heterostructure photodetector with ultrahigh responsivity in the range from 370 to 1550 nm

Abstract

Transition metal dichalcogenides (TMDs) manifest excellent phonon-limited mobility and strong light–matter interaction, which, however, conflict with the long response time and low responsivity of TMD-based photodetectors. The extreme susceptibility of TMDs' electronic qualities to the large density of unscreened disturbances from the SiO₂ substrate accounts for such inconformity. Here, we evaluated the potential of WS₂ for photodetectors by passivating SiO₂ substrates with layered Bi₂Te₃, a representative three dimensional topological insulator. Comparative photoswitching measurements of the WS₂/Bi₂Te₃ photodetector demonstrated its stable and broadband photoresponse from 370 to 1550 nm. Meanwhile, WS₂ and Bi₂Te₃ allied a high responsivity of 30.7 A W⁻¹, a pronounced detectivity of 2.3 × 10¹¹ cm Hz^1/2 W⁻¹ as well as a short response time of 20 ms, which make the device stand out among previously reported WS₂ photodetectors. In fact, the responsivity and detectivity are comparable to those of state-of-the-art commercial Si and Ge photodetectors (R ∼ 0.5 to 0.85 A W⁻¹, D* ∼ 3 × 10¹¹ to 3 × 10¹² cm Hz^1/2 W⁻¹), suggesting its great potential for practical applications. In addition, we also established that the excellent device performance is attributed to the synergy of the passivation of the SiO₂ substrate, efficient carrier separation at the WS₂/Bi₂Te₃ heterointerface and excellent carrier transport along the time-reversal-symmetry protected surface channel of Bi₂Te₃. In summary, these findings suggest that the WS₂/Bi₂Te₃ photodetector will launch a significant advance in next-generation photodetection. Moreover, the interface engineering strategy depicts a universal scenario for development of TMD devices in the future.