Diluted magnetic semiconductors: Actual structure and magnetic and transport properties

An experimental investigation is conducted into electrical-transport, magnetic, optical, and structural properties of GaAs-based diluted-magnetic-semiconductor heterostructures containing a Ga1−xInxAs quantum well and a Mn delta layer 0.5–1.8 ML thick, separated by a GaAs spacer of thickness 3 nm. Ferromagnetic features are observed in the electrical transport and the Hall effect, which involve the flow of holes across the quantum well. They indicate carrier spin polarization in the quantum well. The combined use of high-resolution x-ray diffraction and x-ray reflectivity has made it possible to reliably identify structural-parameter profiles for both the quantum well and the Mn delta layer. It is thus established that the distribution of Mn atoms is nonuniform, both horizontally and vertically. This finding suggests a conception whereby the Mn delta layer divides into nanoscale ferromagnetic-ordering regions and paramagnetic regions. Magnetic and electrical-transport properties of the heterostructures are discussed within this framework.