Local vibrational modes as a probe of activation process in p-type GaN

Raman spectra for a series of Mg-doped GaN films grown by metal organic che mical vapor deposition and annealed in N-2 ambiance at different temperatur es have been investigated. Some local vibrational modes related to hydrogen were observed, showing drastic changes with the annealing temperature. The spectra show clearly that H impurities incorporated in as-grown films, whi ch passivate Mg acceptors, are released from the Mg-N bonding at above simi lar to 600 degrees C, and diffuse in the film to form new chemical bondings . We have also observed a local mode related to activated Mg acceptors. Thi s mode is conveniently used as a probe of the activation process of Mg acce ptors. (C) 1999 American Institute of Physics. [S0003-6951(99)02436-5].