Metal-semiconductor transition and magnetic properties of epitaxially grown MnAs/GaAs superlattices

摘要

We successfully grew epitaxial MnAs/GaAs superlattices at various growth temperatures (T_g) with a periodicity of 5/5 nm using molecular-beam epitaxy and characterized their magnetic and electrical transport properties. Structural analysis shows that the magnetic anisotropy originates from the crystal domain structure of the MnAs layers. The metallic behavior for the sample with T_g=375 deg C systematically changed to semiconducting on increasing T_g up to 540 deg C. The transport properties of thin single layered MnAs films with a thickness of 20 nm showed the same T_g dependency. These observations indicate that the semiconducting characteristics of MnAs/GaAs superlattices are attributable to a radical alteration of the electronic structure of the MnAs layers.