Waveguide-integrated van der Waals heterostructure photodetector at telecom band with high speed and high responsivity

Intensive efforts have been devoted to explore novel optoelectronic devices based on two-dimensional (2D) transition-metal dichalcogenides (TMDCs) owing to their strong light-matter interaction and distinctive material properties [1, 2]. In particular, photodetectors featuring both high-speed and high-responsivity performance are of great interest for a vast number of applications such as high-data-rate interconnects operated at standardized telecom wavelengths [3, 4]. Yet, the intrinsically small carrier mobilities of TMDCs become a bottleneck for high-speed application use [5]. Here, we present high-performance vertical van der Waals heterostructure-based photodetectors integrated on a silicon photonics platform. Our vertical MoTe(2)/graphene heterostructure design minimizes the carrier transit path length in TMDCs and enables a record-high measured bandwidth of at least 24 GHz under a moderate bias voltage of −3 volts. Applying a higher bias or employing thinner MoTe(2) flakes boosts the bandwidth even to 50 GHz. Simultaneously, our device reaches a high external responsivity of 0.2 A/W for incident light at 1300 nm, benefiting from the integrated waveguide design. Our studies shed light on performance trade-offs and present design guidelines for fast and efficient devices. The combination of 2D heterostructures and integrated guided-wave nano photonics defines an attractive platform to realize high-performance optoelectronic devices [6–8], such as photodetectors [9], light-emitting devices [10] and electro-optic modulators [11].