Polarization-sensitive GeSn Mid-Infrared Membrane Photodetectors with Integrated Plasmonic Metasurface

TL;DR

This paper presents a polarization-sensitive mid-infrared photodetector using a GeSn membrane integrated with a plasmonic metasurface, achieving tunable wavelength, enhanced responsivity, and strong polarization contrast.

Contribution

It introduces a novel integration of GeSn membranes with plasmonic metasurfaces for mid-infrared detection, enabling wavelength tunability and polarization sensitivity.

Findings

Wavelength cutoff exceeds 3.0 μm with enhanced responsivity.

Achieves a polarization contrast ratio of approximately 4:1.

Experimental results align well with simulations, confirming design effectiveness.

Abstract

Germanium-Tin (GeSn) semiconductors are promising for mid-infrared optoelectronics owing to their silicon compatibility, tunable bandgap, and potential for room-temperature operation. Released GeSn membranes provide an additional degree of freedom to extend the operation wavelength through epitaxial strain relaxation, while their transferability expands design flexibility. On the other hand, metasurfaces have become an effective strategy to engineer light--matter interaction, and their integration with photodetectors can enhance performance and introduce new functionalities. Here, we demonstrate a mid-infrared photodetector consisting of a transfer-printed Ge$_{0.89}$Sn$_{0.11}$ membrane integrated with an Au plasmonic metasurface. The photodetector exhibits a wavelength cutoff exceeding 3.0~$\mu$m with nearly fourfold increase in responsivity at 2.5~$\mu$m as compared to unreleased films, attributed to Fabry--P\'erot resonance. Furthermore, the integration with an anisotropic metasurface yields detectors with strong polarization sensitivity, achieving a measured contrast ratio of $\sim$4:1 between orthogonal polarizations. Moreover, the operation wavelength of the photodetector can be selectively tuned by varying the geometric scale of the metasurface. The experimental results show excellent agreement with simulations, confirming the effectiveness and versatility of this integrated metasurface--membrane design.