Electron-nuclei spin coupling in GaAs-Free versus localized electrons.

We report on an experimental evidence of a significantly different dynamic nuclear polarization (DNP) for localized and itinerant electrons in n-GaAs. Optically injected spin-polarized electrons are used to generate dynamic nuclear polarization via electron-nucleus hyperfine interaction. Using time resolved Kerr rotation measurements for probing the transient Overhauser field, the DNP time constants for itinerant and localized electrons are extracted to be 10 min and less than 1 min, respectively. This is attributed to a rapid DNP occurring in the vicinity of the donors followed by a delayed nuclear spin polarization in between the donor sites. [ABSTRACT FROM AUTHOR]