Local Vibrational Modes in p-Type GaN Observed by Raman Scattering

Raman spectra for Mg-doped GaN films grown by MOCVD using H2 as the carrier gas are investigated before and after annealing. Some local vibrational modes related to Mg and H are observed, showing drastic changes by annealing. The spectra show clearly that H impurities incorporated in as-grown films, which passivate Mg acceptors, are released from the Mg–N bonding by annealing. When N2 gas is used instead of H2 as the carrier gas, the acceptors are not passivated by H, and p-type conduction is obtained in as-grown films. These features are also clearly observed in the spectra.