Optical spin orientation in group-IV heterostructures

Abstract

We investigate the electron spin polarization upon photoemission from different Si1−xGex heterostructures by means of Mott polarimetry. We demonstrate the possibility to lower the vacuum energy level below the bottom of the conduction band at the Γ point of the Brillouin zone in compressively strained Si1−xGex alloys and we show that the optimization of the stoichiometry of group-IV heterostructures leads to a spin polarization of the electrons in the conduction band up to P=72%±3%. Such a value is not only greater than those attainable in compressively strained pure Ge heterostructures, but it is also comparable to the typical electron spin polarization values of III-V semiconductor heterostructures.