30 GHz plasmonic slot MoTe2 photodetector integrated with silicon photonic circuits at telecom wavelength

Abstract

An experimental demonstration of a waveguide-integrated plasmonic slot photodetector based on MoTe2 with 30 GHz 3 dB roll-off bandwidth at telecom wavelength. To overcome the intrinsic low carrier mobility and weak light-matter interaction when applying two-dimensional material for optoelectronic devices, here we numerically and experimentally show a novel concept of the plasmonic slot structure to eliminate the transit time constant (τ=L^2/μV) from the device which is related to the material mobility. The nanometer-wide plasmonic slot offers a ‘squeezed’ mode that allows the 2d material can effectively absorb the light via band-to-band transitions with an overlap factor (Г) increasing more than 3 times compared to the bare waveguide structure. The ultra-narrow slot width reduces the carriers’ drift route to tens of nanometers and is only limited by the RC time constant. The MoTe₂ serves as the semiconducting light-absorbing material with its layer-dependent bandgap that encompasses the standard O-band wavelength for communications (1,260 nm -1,360 nm). The device's static performance under 1 V bias voltage also shows a high photoresponsivity of 0.8 A/W at 1310 nm with a low dark current of 90 nA. Furthermore, we study the slot width-dependent frequency response and static response to validate our concept, which shows that both the frequency and static response are inversely proportional to the slot width. The concept is not restricted to materials and the platform. This may pave the way for developing high-performance optoelectronic devices with materials that have unique optical and electric properties but suffer from low mobilities.^1–13 It has been shown that introducing plasmonic structures, cavities, resonators, or nanoparticles into waveguide-loaded systems can improve light-matter interactions.^14–17 Still, one of their biggest challenges today is the frequency response of TMDCbased devices for telecommunications or information processing.^18–30 For photodetectors using TMDCs as the lightabsorbing medium, this is particularly crucial.