Spin relaxation and g-factor of two-dimensional electrons in Si/SiGe quantum wells

We investigate spin relaxation and the g-factor of conduction electrons in modulation doped Si/SiGe quantum wells by means of electron spin resonance. We find that both the transverse- and the longitudinal relaxation times are of the order of microseconds. much longer than in III-V compounds. For high mobility. at carrier densities sufficiently far away from the metal-to-insulator transition, both quantities can be explained consistently in terms of the Bychkov-Rashba field, together with the y-factor anisotropy and its dependence on the carrier density. A single value of the BR coefficient,)alpha(BR) = 0.55 x 10(-12) eV cm, explains all data. This value is by more than three orders of magnitude smaller than for III-V compounds owing to the small spin-orbit coupling of Si, The properties found make Si/SiGe quantum structures interesting candidates for quantum Computing. (C) 2002 Elsevier Science B.V. All rights reserved.