Gallium K-edge x-ray absorption study on Mg-doped GaN

Ga K-edge x-ray absorption measurements were employed to investigate Mg-dop ing effects in GaN samples. Strong polarization-dependent x-ray absorption near-edge structures become less pronounced with increasing doping concentr ation, indicating the formation of a mixing-phase structure of cubic and he xagonal phases. Analysis of the extended x-ray absorption region of the spe ctra revealed doping-related defects such as vacancies, substitutions, and interstitial occupations. They were formed anisotropically in the crystal c axis direction and its perpendiculars. Disorderliness arising from phase m ix and defects is believed to have lowered the Debye temperature of the dop ed GaN films and caused the destructive interference of the absorption fine -structure oscillation functions. These effects were taken into account for the observed large coordination number reductions in our samples. (C) 2001 American Institute of Physics.