Giant g-factor in metamorphic InAsSb/InSb superlattices with ultra-narrow bandgap

Semiconductor materials with high g-factor are potential key component for spintronic and quantum information processing devices. Enhancement of electron g-factor is promoted by admixing of the valence band states to the conduction band ones and is typically high in narrow bandgap materials with large spin orbit coupling. In type II superlattices (SLs) where the bandgap can be reduced by increasing the SL period, g-factor enhancement is impeded by spatial separation between the conduction and valence band states. Here we present metamorphic InAsSb/InSb SLs, where the effective lattice constant can be controlled and ultra-narrow bandgaps can be realized in SLs with thin layers. In the metamorphic SLs the overlap between electron and hole states can be effectively varied, so g-factor can be widely tuned from 30 to 110. A giant g-factor of 104, which is nearly twice larger than that of InSb, was extracted from polarization-resolved far-infrared magneto absorption spectra. The Landau levels in InAsSb/InSb SLs are found nearly 100% spin-polarized at low magnetic fields.