P‐type conductivity in as‐grown Mg‐doped GaN films grown by reactive molecular beam epitaxy technique which employs ammonia as the nitrogen source is reported. Doping level and mobility of the films up to 4.5×1017 cm−3 and 6 cm2/V s, respectively, have been achieved without any post‐growth treatments. The photoluminescencespectra show both band edge and Mg‐related emission at room temperature. Neither annealing in nitrogen ambient furnace nor rapid thermal annealing was found to have any discernible influence on the electrical properties of the films. More than 6% of incorporated Mg was activated for the samples with relatively low Mg concentration. The measured activation energy of Mg acceptor was 160±5 meV.