Ferromagnetic Mn modulation-doped two-dimensional hole systems

Mn modulation-doped strain relaxed In0.75Ga0.25As/In0.75Al0.25As single quantum-well (SQW) structures on (001)GaAs with an embedded InAs channel are fabricated by molecular beam epitaxy. The properties of the magnetic two-dimensional hole system were investigated by magnetotransport measurements up to 19 T in the temperature range from 50 mK to room temperature. In the low-temperature regime typical features of the quantum Hall effect like quantized plateaus at the Hall resistance and Shubnikov-de Haas oscillations in the longitudinal resistance are observable. The resistance at B = 0 T shows a distinct temperature dependence, and at low temperatures, a large negative magnetoresistance. Furthermore, a hysteretic behavior and jumps in the resistance below 300mK and around B = 0 T can be observed for an asymmetric QW structure. (C) 2007 Elsevier B.V. All rights reserved.