Theory of electron spin relaxation in ZnO

Abstract

Doped ZnO is a promising material for spintronics applications. For such applications, it is important to understand the spin dynamics and particularly the spin relaxation times of this II-VI semiconductor. The spin relaxation time ${\ensuremath{\tau}}_{s}$ has been measured by optical orientation experiments, and it shows a surprising nonmonotonic behavior with temperature. We explain this behavior by invoking spin exchange between localized and extended states. Interestingly, the effects of spin-orbit coupling are by no means negligible, in spite of the relatively small valence-band splitting. This is due to the wurtzite crystal structure of ZnO. Detailed analysis allows us to characterize the impurity binding energies and densities, showing that optical orientation experiments can be used as a characterization tool for semiconductor samples.