Abstract
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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xx</sub> , ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">yy</sub> and ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</sub> ), 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.
Highlights
S ILICON (Si) and Germanium (Ge) are widely used in photonics integrated circuits
We focus on the modeling of highly strained Ge crossbeams
Such results are used to calculate the bandgap spatial distribution in Ge crossbeams by converting the strain mapping into bandgap mapping for the L and Γ valley, which are the most significant transitions needed to evaluate the potential of these devices for laser applications
Summary
S ILICON (Si) and Germanium (Ge) are widely used in photonics integrated circuits. the indirect bandgap of these elements prevents them to be used as efficient lightsources. Different technologies have already demonstrated the possibility to reach the needed strain to transform the Ge indirect bandgap to a direct one [13]–[15] Among these techniques, strain redistribution in crossbeam [15], [16] appears as a very promising method since cavity oscillation have been recently demonstrated with a reduction of the spectral resonances at around 2 μm wavelength with strain [17]. We first study the modeling of strained bulk Ge for all the possible strain configurations in suspended layers Such results are used to calculate the bandgap spatial distribution in Ge crossbeams by converting the strain mapping into bandgap mapping for the L and Γ valley, which are the most significant transitions needed to evaluate the potential of these devices for laser applications. We highlight here the relation between those two fundamental parameters and we present a relevant method to evaluate the potential of crossbeam designs for laser applications
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