Waveguide-Coupled Mid-Infrared GeSn Membrane Photodetectors on Silicon-on-Insulator

Silicon photonics has thrived in telecommunications over recent decades, and its extension to the mid-infrared range has the potential to unlock valuable opportunities for sensing, imaging, and free-space communications. With this perspective, germanium-tin (GeSn) alloy has been extensively investigated as a silicon-compatible semiconductor with bandgap tunability that covers this entire spectral range. Indeed, a variety of GeSn-based high-performance optoelectronic devices have been demonstrated, confirming the potential of this system for mid-infrared applications. However, the integration of these devices onto silicon photonic platforms remains underexplored. Herein, we demonstrate the fabrication and integration, through transfer-printing, of strain-relaxed GeSn membranes onto silicon-on-insulator waveguides to create integrated detectors operating up to 3.1 $\mu$m at room temperature. Two different designs of waveguide structures are evaluated to study the coupling efficiency between the passive structures and the active membrane detector. A responsivity reaching 0.36 A/W at an operation wavelength of 2.33 $\mu$m is measured under a bias of 1 V. Moreover, the fabrication resulted in multiple working devices exhibiting similar performance using a single transfer printing step, demonstrating the scalability of the proposed approach.