Mn-doped cubic GaN films were grown by plasma-assisted molecular beam epitaxy on GaAs (001) substrates. There was a strong influence of the Ga:N ratio on the Mn incorporation and a dramatic increase in the Mn concentration was observed for the layers grown under N-rich conditions. Hall-effect measurements unambiguously showed that the GaMnN samples had strong p-type conductivity. For both N-rich and Ga-rich growth conditions a bulk hole density of about 10(18) cm(-3) was achieved with a corresponding mobility of > 300 cm(2) V-1 s(-1). This compares very favorably with other values reported for p doping of cubic GaN doped with C, suggesting that Mn may be a very suitable dopant for GaN-based electronic structures. The apparent values of ionization energy for Mn were around 50 meV, which is much shallower than for C or Mg in cubic GaN. In addition to a small high temperature ferromagnetic signal, a ferromagnetic correlation was detected among the remaining Mn ions at low temperatures, which is assigned to the onset of hole-mediated ferromagnetism in cubic GaMnN. (c) 2005 American Vacuum Society.