We present the results of the epitaxial overgrowth of magnetic (MnGa)As-cluster structures with GaAs. (AlGa)As and AlAs using metal organic vapor phase epitaxy (MOVPE). The structural differences ill the overgrowth are investigated by means of atomic force microscopy (AFM) combined with transmission electron microscopy (TEM), in particular. to proof the successful overgrowth of the cluster layers with AlAs. Out of these experiments a first model for the overgrowth is developed. Measurements using a SQUID-magnetometer confirm the existence of ferromagnetism above room temperature in the cluster layers after overgrowth: hoe er. other magnetic properties its the coercitive field are influenced by the overgrowth process, (C) 2002 Elsevier Science B.V. All rights reserved.