Modeling and design of an electrically pumped SiGeSn microring laser

We present a suspended SiGeSn microring laser design that enables strain relaxation of the material layer stack, electrical pumping and adequate heat sinking. Using both strain and composition as two degrees of freedom to engineer the band structure, a direct bandgap is obtained in the gain material of a double heterostructure layer stack, and the L- to Γ-valley energy difference increased to 78 meV, by 66% compared to a non-underetched structure. The temperature dependent current threshold is modeled for the designed device and determined to be 18 kA/cm2 at 50 K. The fabrication process is outlined and first experimental electroluminescence results indicating the effectiveness of our approach are reported. At the time this proceedings paper is being submitted, electrically pumped lasing has also been achieved with a similar structure, with results that will be reported in a future publication.