Annealing effect on the electron spin dynamics in heavily Mn-doped (Ga,Mn)As

Abstract

A temperature- and photo-excitation-density-dependent electron spin dephasing process has been studied by time-resolved magneto-optical Kerr effect (TR-MOKE) measurements for heavily-doped (Ga,Mn)As after appropriate annealing treatment. Unlike the as-grown (Ga,Mn)As in which s-d scattering is dominant for spin dephasing at low temperature, the exchange scattering induced by Mn ions is efficiently suppressed after annealing. For annealed (Ga,Mn)As, the p-d exchange coupling proves to be important for the electron spin dephasing process. Moreover, the Coulomb scattering arising from the weakly-localized holes and Mn impurities is revealed to play an important role in the electron spin dephasing after annealing. Our results demonstrate that the impurityinduced disorder plays a significant role in the electron spin-dephasing process in (Ga,Mn)As when Mn is over doped by as much as 15%, which is a critical issue that needs to be considered to achieve high-quality (Ga,Mn)As thin films with a higher Curie temperature TC and better functionality.