Electron-spin polarization near the Fermi level in n-type modulation-doped semiconductor quantum wells

We study the spin polarization of optically created electrons near the Fermi energy in an n-type modulation-doped single quantum well. In our system the Fermi level is slightly above the second confined conduction subband. The results reveal that electrons optically created close to the Fermi level partially conserve their spin polarization, despite the presence of the electron gas. Data obtained by changing the excitation intensity show that exchange interaction among optically created electrons and holes dominates the spin flip processes in the vicinity of the Fermi edge.