Modeling of the Bandgap Distribution in Bi-Axially Strained Germanium Crossbeam for Laser Applications

High tensile strained Ge cavities in crossbeam are promising for the development of integrated laser sources on Si. However, the optimization of such cavities remains more challenging than the uniaxial beams. Indeed, the spatial distributions of both the optical field and the material gain have to be simultaneously defined by the nuances of complex cavity geometry. In this work, we simulate spatial distribution of the bandgap in bi-axially strained Ge crossbeams. Starting from stress map calculations, we achieved the bandgaps mapping for all possible suspended strain configuration (i.e ϵ xx , ϵ yy and ϵ xy ), when merged with bandgaps modeling. A trade-off is evidenced between membrane orientation and arm curvature to reach the largest possible volume of amplifying material. Our work highlights the fundamental importance of these two parameters for Ge crossbeam design and presents a relevant modeling tool to define suitable cross designs for laser applications.