High-speed uni-traveling-carrier photodiodes on silicon nitride

Integrated photonics is an emerging technology for many existing and future telecommunication and data communication applications. One platform of particular interest is silicon nitride (SiN), thanks to-among others-its very low-loss waveguides. However, it lacks active devices, such as lasers, amplifiers, and photodiodes. For this, hybrid or heterogeneous integration is needed. Here, we bring high-speed uni-traveling-carrier photodiodes to a low-loss SiN-platform by means of micro-transfer-printing. This versatile technology for heterogeneous integration not only allows very dense and material-efficient III-V integration but also eases the fabrication, yielding high-performance detectors. The waveguide-coupled photodiodes feature a responsivity of 0.3 A/W at 1550 nm, a dark current of 10 nA, and a bandwidth of 155 GHz at a low bias. At zero bias, a record bandwidth of 135 GHz is achieved. We further demonstrate that this integrated detector can be used for direct photomixing at terahertz frequencies. A back-to-back communication link with a carrier frequency of around 300 GHz is set up, and data rates up to 160 Gbit/s with a low error vector magnitude are shown, showcasing a near-identical performance at zero bias.