GeSn Quantum Wells for Room‐Temperature Mid‐Infrared Lasing on Si and on Insulator Platforms

Recent advances in group-IV materials, particularly germanium–tin (GeSn) alloys, have reinvigorated the pursuit of CMOS-compatible light sources. The optical performance of GeSn is governed by the coupled effects of Sn composition and lattice strain, which together dictate optical gain and the maximum operating temperature. Here, through a tailored heterostructure design and epitaxial strategy, we realize GeSn multi-quantum-well (MQW) heterostructures with ∼15 at.% Sn in the wells and systematically investigate their performance on two distinct platforms: GeSn on-Si bulk and GeSn-on-insulator. By engineering the lattice strain from compressive to tensile, we reveal the fundamental trade-off between lasing threshold and maximum operating temperature. The GeSn-on-insulator MQW platform delivers outstanding performance, enabling mid-infrared lasing at room temperature (293 K) with a threshold of 500 kW cm‾² in a simple mesa cavity, while the tensile-strained counterpart achieves a lower threshold of 8 kW cm‾² at 77 K but sustains laser emission only up to 265 K. These results indicate that GeSn MQWs are a viable group-IV gain medium for mid-infrared lasing and highlight their potential for integration into CMOS-compatible silicon photonic circuits.