Electrical characterization of Mg-related energy levels and the compensation mechanism in GaN : Mg

We investigated GaN:Mg samples grown by metalorganic chemical vapor deposit ion using various electrical measurement techniques. Annealing of as-grown samples for different duration of time gives gradual activation of accepter s. Conductance measurements of the annealed samples show the presence of a hole trap with concentration directly proportional to the electrically acti ve acceptor concentration in the samples. This trap is the shallowest one i n our samples with activation energy 130 from the valence band. We attribut e it to an Mg acceptor. Electron traps observed in optical deep-level trans ient measurements have too weak concentrations to influence the free carrie r concentration. We conclude that the hole conductivity observed in the ann ealed GaN samples is due to thermal dissociation of hydrogen from passivate d Mg accepters. Most of the Mg concentration in the samples however remains electrically inactive. (C) 1999 Elsevier Science B.V. Ail rights reserved.