Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks

GeSn alloys offer a promising route towards a CMOS compatible light source and the realization of electronic-photonic integrated circuits. One tactic to improve the lasing performance of GeSn lasers is to use a high Sn content, which improves the directness. Another popular approach is to use a low to moderate Sn content with either compressive strain relaxation or tensile strain engineering, but these strain engineering techniques generally require optical cavities to be suspended in air, which leads to poor thermal management. In this work, we develop a novel dual insulator GeSn-on-insulator (GeSnOI) material platform that is used to produce strain-relaxed GeSn microdisks stuck on a substrate. By undercutting only one insulating layer (i.e., Al₂O₃), we fabricate microdisks sitting on SiO₂, which attain three key properties for a high-performance GeSn laser: removal of harmful compressive strain, decent thermal management, and excellent optical confinement. We believe that an increase in the Sn content of GeSn layers on our platform can allow us to achieve improved lasing performance.