Zinc-blende Ga1-xMnxN epilayers grown by plasma-assisted molecular beam epitaxy as a function of Ga flux are assessed using a variety of structural characterisation techniques. The Ga:N ratio was found to have a dominant impact on the zinc-blende Ga1-xMnxN epilayer growth rate and resultant composition, morphology and rnicrostructure. A maximum growth rate and an improved microstructure are associated with growth under slightly Ga-rich conditions. A reduced growth rate and enhanced Mn incorporation are associated with growth under slightly N-rich conditions. alpha-MnAs inclusions and voids extending into the GaAs buffer layer were observed in all cases, however they are considered not to affect the layer electrical and magnetic properties. (c) 2005 Elsevier B.V. All rights reserved.