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

## TL;DR

This paper demonstrates a high-speed, high-responsivity photodetector using van der Waals heterostructures integrated on silicon photonics, achieving record bandwidths up to 50GHz at telecom wavelengths.

## Contribution

It introduces a vertical MoTe2/graphene heterostructure design that minimizes carrier transit time, enabling record-high bandwidths in integrated 2D material-based photodetectors.

## Key findings

- Bandwidth of at least 24GHz at -3V bias
- Bandwidth boosted to 50GHz with higher bias or thinner flakes
- Responsivity of 0.2A/W at 1300nm

## Abstract

Intensive efforts have been devoted to exploit novel optoelectronic devices based on two-dimensional (2D) transition-metal dichalcogenides (TMDCs) owing to their strong light-matter interaction and distinctive material properties. 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. Yet, the intrinsically small carrier mobilities of TMDCs become a bottleneck for high-speed application use. Here, we present high-performance vertical van der Waals heterostructure-based photodetectors integrated on a silicon photonics platform. Our vertical MoTe2/graphene heterostructure design minimizes the carrier transit path length in TMDCs and enables a record-high measured bandwidth of at least 24GHz under a moderate bias voltage of -3 volts. Applying a higher bias or employing thinner MoTe2 flakes boosts the bandwidth even to 50GHz. Simultaneously, our device reaches a high external responsivity of 0.2A/W for incident light at 1300nm, 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, such as photodetectors, light-emitting devices and electro-optic modulators.