  Recent interest in very thin single phase Ga1-xMnxN dilute magnetic layers
increased needs for precise, non-destructive, and relatively fast
characterization methods with key issues being the macroscopic lateral Mn
distribution and the absolute values of Mn concentration x. We report on
resonantly enhanced UV Raman scattering studies of high quality Ga1-xMnxN
layers grown on GaN templated sapphire by molecular beam epitaxy with 4 < x <
9%. The main advantage of the UV excitation is the restriction of the light
penetration depth to nearly a hundred nanometers, eliminating signal from the
GaN buffer. Under this conditions we determine the dependence of the 1LO phonon
frequency on x, what allows for a fine mapping of its lateral distribution over
the entire surface of the samples. Our Raman scanning clearly confirms
substantial lateral distribution of Mn atoms across the layer, which is radial
with respect to its center. From the established distributions in two
deliberately chosen layers the magnitude of the optimal growth temperature for
most efficient Mn atoms incorporation in epitaxial GaN has been confirmed. It
is shown that the combination of the 1LO line width and its energy provides
assessment of the crystalline quality of the investigated layers.
