Study of critical optical confinement factor for GeSn-based multiple quantum well lasers

Abstract

SiGeSn material is of great interest for the development of all-group-IV lasers on a Si substrate. While GeSn-based lasers have been reported worldwide, probing the fundamental limit to lase is highly desirable to reveal the material capability as a gain medium. In this work, three GeSn-based multiple quantum well lasers, with four wells, six wells, and ten wells, were characterized. The four-well device cannot achieve lasing due to the thin active region (thickness of 81 nm), resulting in insufficient optical confinement factor. With thicker active region, both six-well (92 nm) and ten-well (136 nm) devices show clear lasing output. The ten-well sample exhibits a higher lasing temperature of 90 K. The finding of this work reveals the fundamental limit of the required optical confinement factor to achieve lasing for a Fabry-Pérot cavity edge emitting laser devices.