INTERFACIAL REACTIONS BETWEEN NICKEL THIN-FILMS AND GAN

Thin Ni films on GaN were annealed at temperatures between 400 and 900 degrees C in N-2, Ar, and forming gas and were analyzed using glancin g angle x-ray diffraction and Auger depth profiling, The first indicat ion of an interfacial reaction was found after an anneal at 600 degree s C for 1 h, after which Ga was observed to be dissolved in the face-c entered cubic Ni film. The extent of dissolution increased with contin ued annealing. After annealing at 750 degrees C for 1 hr in tither N-2 or Ar, greater intermixing occurred. The reaction product was either Ni3Ga or face-centered cubic Ni with dissolved Ga. Annealing at 900 de grees C resulted in the formation of the B2 phase NiGa. it was clear f rom Auger depth profiles that the reacted film contained significantly more Ga than N and that N-2 gas was released to the annealing environ ment, even when the samples were annealed in N-2 gas at 1 arm. Thus, a trend of increasing Ga content in the reacted films was observed with increasing temperature. The observed reactions are consistent with th e thermodynamics of the Ni-Ga-N system. (C) 1997 American Institute of Physics.