NANOMETER-SCALE MAGNETIC MNAS PARTICLES IN GAAS GROWN BY MOLECULAR-BEAM EPITAXY

Spherical MnAs ferromagnetic particles with controllable diameters (5- 30 nm) are embedded in a high quality GaAs matrix. The particles are f ormed in a two step process consisting of the epitaxy of a homogeneous Ga1-xMnxAs layer at low temperatures using molecular beam epitaxy fol lowed by phase separation upon annealing. During the annealing step, t he excess arsenic in the as-grown film forms magnetic MnAs precipitate s with the Mn from the Ga1-xMnxAs lattice. Structural and room-tempera ture magnetic properties of the heterogeneous GaAs:MnAs films are desc ribed. The magnetic MnAs rich layers can be incorporated into semicond uctor heterostructures as demonstrated by growing (GaAs/AlAs) multiple quantum well structures in combination with GaAs:MnAs layers. (C) 199 6 American Institute of Physics.