Strain engineering of transverse electric and transverse magnetic mode of material gain in GeSn/SiGeSn quantum wells

Abstract

8-band k · p Hamiltonian together with envelope function approximation and planewave expansion method are applied to calculate the electronic band structure and material gain for Ge 1−w Sn w /Si y Ge 1−x−y Sn x /Ge 1−w Sn w quantum wells (QWs) grown on virtual Ge 1-z Sn z substrates integrated with Si platform. It is clearly shown how both the emission wavelength in this material system can be controlled by the content of virtual substrate and the polarization of emitted light can be controlled via the built-in strain. In order to systematically demonstrate these possibilities, the transverse electric (TE) and transverse magnetic (TM) modes of material gain, and hence the polarization degree, are calculated for Ge 1−w Sn w /Si y Ge 1−x−y Sn x /Ge 1−w Sn w (QWs) with the strain varying from tensile (ε = +1.5%) to compressive (ε = −0.9%). It has been predicted that the polarization can be changed from 100% TE to 80% TM. In addition, it has been shown that Si y Ge 1−x−y Sn x barriers, lattice matched to the virtual Ge 1-z Sn z substrate (condition: y = 3.66(x-z)), may ensure a respectable quantum confinement for electrons and holes in this system. With such material features Ge 1−w Sn w /Si y Ge 1−x−y Sn x /Ge 1−w Sn w QW structure unified with Ge 1-z Sn z /Si platform may be considered as a very prospective one for light polarization engineering.