Advances in GeSn alloys for MIR applications

Silicon photonics is widely used for near InfraRed (IR) applications up to 1.6 µm. It plays a key role in short-range optical data communications. However, silicon photonics does not really address mid-IR applications, particularly in the 1.6–5 µm wavelength range. This spectral region is essential for environmental/life sensing and safety applications relying on the optical features of molecular vibrations, the aim being to discern and categorize complex chemical entities. Growing markets for such analysis prioritise sensitivity, specificity, compactness, energy-efficient operation and cost effectiveness. The need for a CMOS-compatible integrated photonic platform for the mid-IR is obvious. Such fully-group-IV semiconductor platform should include low-loss guided interconnects, detectors, modulators and, critically, efficient integrated light sources. This paper provides a comprehensive review of recent advances in GeSn-based mid-IR silicon-compatible devices, including optically and electrically pumped lasers, light-emitting diodes and photodetectors. It also discusses the principles underlying these developments, with focuses on material growth techniques and processing methods.