Optical Spin Orientation In Group-Iv Heterostructures

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 Gamma 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. (C) 2013 American Institute of Physics.