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

After thriving in telecommunications over recent decades, silicon photonics is now being extended into the mid-infrared range, where it has the potential to unlock a wide range of valuable opportunities in sensing, imaging, and free-space communications. In view of this perspective, the 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 at wavelengths up to 3.1 μm 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 operating wavelength of 2.33 μm 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.