Effect of Low Temperature Annealing on the Magnetic Properties of Ga1?xMnxAs/GaAs Superlattices

We have studied the effect of low-temperature (LT) annealing on the properties of Ga_1–xMn_xAs/GaAs superlattices (SLs). One SL contained GaAs layers doped by Be (which acts as a p-type dopant), while the GaAs layers of the other SL were undoped. The Be-doped SL exhibited a coercive field (H_C) three times larger than the undoped SL, and showed a much more robust remanent magnetization (M_r). While the effect of LT annealing on the undoped SL was relatively minor, magnetic properties of the Be-doped SL changed significantly after annealing. The coercive field of the Be-doped SL was reduced about three times, becoming comparable to that of the undoped SL. After annealing the temperature dependence of M_r in the Be-doped SL also became similar to the undoped SL. We discuss the effect of LT annealing on the magnetic properties of the two SL systems in terms of inter-diffusion of carriers, and of the reduced sensitivity to annealing characteristic of capped structures.