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

Abstract

Intensive efforts have been devoted to exploit novel optoelectronic devices based on two-dimensional (2D) transition-metal dichalcogenides (TMDCs) owing to their strong lightmatter 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 highperformance optoelectronic devices [6][7][8], such as photodetectors [9], light-emitting devices [10] and electro-optic modulators [11].During the last decade, two-dimensional (2D) materials such as graphene and transition-metal dichalcogenides (TMDCs) have shown great promise for a wide range of photonic and optoelectronic applications [12][13][14]. 2D devices have the potential to outperform established and more mature technologies, particularly in terms of form * These authors contributed equally. † leuthold@ethz.ch ‡ lnovotny@ethz.ch factor, operating conditions and cost-effectiveness. The possibility to integrate 2D materials without constraints of crystal lattice matching is disruptive, as it tremendously simplifies manufacturing and increases possible material combinations. Graphene, which has been widely used for successful 2D device implementations [15][16][17][18][19][20], has an intrinsically weak photosensitivity, though its interaction with light can be enhanced using silicon-based integrated photonics, such as optical resonators [17] or waveguides [21]. Nevertheless, graphene-based devices suffer from other issues stemming from its gapless nature, e.g., large dark currents for photodetectors. Alternatively, TMDCs, a semiconducting class of 2D materials, hold great promise for high-performance optoelectronic devices due to their intrinsically strong light-matter interactions [22]. Yet, the integration with a silicon-based platform is challenging, because direct band-to-band transition energies of TMDCs fall within the absorption band of silicon. Despite of this, few attempts have been made towards the integra...

Hybrid silicon photonic devices with two-dimensional materials

“…The vdW integration could enable artificial heterostructures and superlattices with atomically-clean and electronicallysharp interfaces between highly disparate materials [191]. Recently, Nicolaus et al demonstrated a waveguide integrated MoTe 2 -graphene vdW heterostructure photodetector [192], for which the responsivity is about 0.2 A/W at 1300 nm and the normalized photo-dark-current (NPDR) ratio is almost an order of magnitude than pure-graphene photodetectors due to the bandgap in MoTe 2 . Moreover, the vertical MoTe 2 -graphene heterostructure design minimizes the carrier transit path length in TMDs and enables a record measured bandwidth of >24 GHz.…”

2D materials integrated with metallic nanostructures: fundamentals and optoelectronic applications

“…Black phosphorus could be another promising material in terms of photodetection owing to its direct and tunable bandgap, as well as the high sensitivity in the near-and mid-infrared regimes [224][225][226]. Black phosphorus analogs, such as Bi, Te, and SnS, have also been [233] Exfoliated graphene and hBN Si strip waveguide 0.36 42 Schuler et al [234] Exfoliated graphene Si slot waveguide 0.076 65 Flöry et al [235] vdWs heterostructure Si strip waveguide 0.2 27 Goykhman et al [236] CVD graphene Si-Au Schottky structure 0.37 Not mentioned Ding et al [35] CVD graphene Plasmonic slot waveguide 0.36 >110 Ma et al [221] CVD graphene Si 3 N 4 strip waveguide with metallic bowtie structures 0.5 >110 Guo et al [237] CVD graphene Si-plasmonic hybrid waveguide 0.4 >40 Chen et al [222] Exfoliated BP Si-plasmonic 3D integration 10 0.150 applied in the photodetection, but with moderate responsivity and response speed [196,227,228]. Multiple works of the BP photodetector based on both free-space and waveguide-integrated schemes were reported.…”

Atomic‐Precision Repair of a Few‐Layer 2H‐MoTe2 Thin Film by Phase Transition and Recrystallization Induced by a Heterophase Interface

“…The large‐scale semiconducting 2H‐MoTe 2 with single‐crystalline domain size up to hundreds of micrometer has been synthesized by the unique phase transition between 1T'‐ to 2H‐MoTe 2 . [ 13 ] Due to the moderate bandgap of few‐layer 2H‐MoTe 2 of 1.0 eV, ambipolar charge transport [ 14 ] and optical devices operated at standardized telecom wavelengths [ 15 ] have been reported using MoTe 2 . Monolithic integration allows both the electronics and the optical devices to be integrated with van der Waals MoTe 2 in a single growth process.…”