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.

The effects of strain and composition on the conduction-band offset of direct band gap type-I GeSn/GeSnSi quantum dots for CMOS compatible mid-IR light source

“…The phenomenon is due to the strain conversion from tensile strain to compressive strain in the GeSn QD with the increasing of Sn content in the QD. Besides, the built-in strain of GeSn QDs will change the polarization of light from GeSn QDs which has been theoretically investigated by GeSn /GeSnSi quantum well recently [47]. In many applications, non-polarization is preferred.…”

“…Figure 6 shows the band alignment of the Ge 0.875 Sn 0.125 /Ge 0.684 Sn 0.166 Si 0.150 quantum well with a low b Γ,SiSn (4 eV) and the energy levels of the ground states (dashed line) which are calculated by 8-band k•p method and single-band effective mass method. To compare the results to the recent publication on GeSn/ GeSnSi QW [47] more directly, the parameters and Hamiltonian for the 8-band k•p modeling are taken from the reference [47]. The conduction band offset is as high as 273 meV which is more than 5 times of the results calculated with a high b Γ,SiSn (b Γ,SiSn =13.6 eV) due to the increased energy of the conduction band of the GeSnSi barrier.…”

Optical Gain Characteristics of BGaAs/GaP Quantum Wells

“…Similarly to our previous works [22], [23], [55], [56], band-structures of bulk crystals are obtained within the 8-band k•p model for zinc-blende symmetry including the Bir-Pikus Hamiltonian for strain effects [57]. Here, the strain in the thin layer is homogenous with the unstrained substrate as its source.…”

“…Next, the QWs band-structures are applied to the calculation of the material optical gain spectra of the QWs. The spectra are calculated within the standard approach based on the Fermi's golden rule [63], as in our previous works [22], [23], [55], [56].…”

“…Furthermore, lasing actions of bulk crystals or QWs inside various micro resonators integrated with the Si technology have been demonstrated in recent studies [16]- [21]. Simultaneously with the advances in the technology, many theoretical researches predicted and analyzed the optical gain of GeSn-based low-dimensional structures [22]- [29] to set up new possibilities in further development of the system. Other popular approaches are based either on silicon itself (Er doping, stimulated Raman scattering, Si nanoparticles) [3], [4], [30] or III-V semiconductor alloys that are already widely used in the light emitting applications (hybrid structures, heteroepitaxy of nanopillars or nanoneedles) [2], [3], [30]- [32].…”