Spin relaxation times and spin-dependent transport of silicon 2DEG and donors in high magnetic fields

We measured the spin-lattice relaxation ($T_1$) and spin coherence ($T_2$) times of the two-dimensional electron gas (2DEG) and neutral donors in a silicon field-effect transistor by pulsed electrically detected magnetic resonance at $\approx3.4\:$T. The 2DEG $T_1$ varies between $\approx200-800\:$ns depending on the carrier density with an in-plane magnetic field configuration, but remains constant at $\approx400\:$ns with an out-of-plane field configuration. On the other hand, $T_2\approx50-150\:$ns for all carrier densities and both field orientations. The neutral donor $T_1$ and $T_2$ are found to be similar to that of the 2DEG. At even higher out-of-plane magnetic fields of $8-12\:$T, Landau levels are clearly resolved in transport measurements and both the 2DEG and donor EDMR signals show corresponding oscillatory behavior as the carrier density is varied. We attribute this behavior to the alignment of the Fermi level with spin-split and different indexed Landau levels.