Transport and magnetic properties of Mn- and Mg-implanted GaAs layers

Mn-doped GaAs layers were fabricated by direct ion implantation into semi-insulating GaAs (1 0 0) substrates. The implanted samples were annealed at temperatures Ta=700–800°C. At these temperatures MnAs clusters are formed in GaAs due to decay of the supersaturated solid solution of Mn in GaAs. Additional Mg ion implantation was used to provide an enhancement of p-type doping in (Ga,Mn)As layers. Temperature dependence of resistance was measured between 4.2 and 300 K, and the Hall effect was measured at temperatures of 4.2–200 K. Anomalous Hall effect and ferromagnetic behavior have been found for all samples. An enhanced positive magnetoresistance was also observed at T>30K.