Structural and transport properties of GaAs/δ-Mn/GaAs/InxGa1−xAs/GaAs quantum wells

We report results of investigations of the structural and transport properties of GaAs/Ga1−xInxAs/GaAs quantum wells (QWs) having a 0.5–1.8 monolayer (ML) thick Mn layer, separated from the QW by a 3 nm thick spacer. The structure has hole mobility of about 2000 cm2 (V s)−1, being by several orders of magnitude higher than in known ferromagnetic two-dimensional (2D) structures. The analysis of the electro-physical properties of these systems is based on detailed study of their structure by means of high-resolution x-ray diffractometry and glancing-incidence reflection, which allow us to restore the depth profiles of the structural characteristics of the QWs and thin Mn-containing layers. These investigations show the absence of Mn atoms inside the QW. The quality of the structures was also characterized by photoluminescence spectra from the QWs. The transport properties reveal features inherent to ferromagnetic systems: a specific maximum in the temperature dependence of the resistance and the anomalous Hall effect (AHE) observed in samples with both ‘metallic’ and activated types of conductivity up to ∼100 K. AHE is most pronounced in the temperature range where the resistance maximum is observed. The results are discussed in terms of the interaction of 2D-holes and magnetic Mn ions in the presence of large-scale potential fluctuations related to the random distribution of Mn atoms. The AHE values are compared with calculations taking into account the ‘intrinsic’ mechanism in ferromagnetic systems.