Passivation and activation of Mg acceptors in heavily doped GaN

Electron paramagnetic resonance measurements are used to monitor the passivation and activation of the Mg-related acceptor in GaN doped with different concentrations of Mg, up to 2 x 10 20 cm(-3). Samples were annealed in either forming gas (H-2:N-2) or pure N-2 between 200 and 900 degrees C. As expected, the Mg-related EPR signal is reduced by at least a factor of ten during the forming gas treatment; while the pure N-2 environment revives the signal. However, the study also shows that reactions between Mg and hydrogen occur at a temperature as low as 525 degrees C in the 10(20) cm(-3) Mg doped samples; while in more lightly doped samples, temperatures greater than 700 degrees C are required to observe changes in the Mg signal intensity. While the observations support the model in which a hydrogen atom ionizes at the Mg impurity and the remaining proton bonds at a near neighbor, the different temperature dependence suggests that hydrogen diffusion is affected by the increased Mg concentration. (C) 2011 American Institute of Physics. [doi:10.1063/1.3626461]