Effects of hydrogen plasma treatment at 250 degreesC on electrical properties and deep level spectra of the p-AlGaN films with the Al mole fraction of x = 0.15 are reported. It is shown that the concentration of Mg acceptors is strongly (about an order of magnitude) decreased after such a treatment, most likely due to hydrogen passivation of acceptors. It is also shown that there are in fact two closely spaced in energy shallow acceptors and that the ones dominant in the virgin and Mg-related samples are more effectively passivated than the others. Hydrogen plasma treatment also leads to suppression of deep nonradiative recombination centers as evidenced by the increase in the microcathodoluminescence intensity. (C) 2004 American Vacuum Society.