Mg-doped GaN films are grown by metallorganic chemical vapor deposition and characterized by photoluminescence (PL), Hall-effect measurements, and secondary-ion mass spectroscopy (SIMS). Optimum Mg acceptor activation annealing conditions were determined to be 750 degrees C for 10 min in a nitrogen ambient. The free-hole concentration and electrical conductivity of these layers reach their maximum values at relatively low bis(cyclopentadienyl)magnesium (Cp2Mg) flow rates. The PL peak wavelength and intensity also vary with Cp2Mg flow rate, with the shortest emission wavelength and highest intensity occurring in samples with the highest hole concentration and electrical conductivity. SIMS data on n-p-n epitaxial layer’s demonstrate abrupt changes in the dopant concentration for Mg.