A comprehensive Raman study was made of defects which appeared, in Raman spectra, as sharp and intense lines in the region from 95 to 250/cm. These lines decreased almost exponentially in intensity, with increasing temperature, and were excitable only in the range of 2.0 to 2.5eV. Their temperature behavior seemed to be incompatible with vibronic excitations, but suggested an electronic scattering mechanism. However, magnetic-field and high-pressure dependent Raman measurements contradicted this suggestion. It was instead shown that all of the lines were caused by a vibrational Raman scattering in which the temperature dependence was due to resonance processes. It was demonstrated, by means of doping experiments, that the responsible defects were related to As impurities.

Raman Scattering from Defects in GaN. H.Siegle, A.Kaschner, A.Hoffmann, I.Broser, C.Thomsen, S.Einfeldt, D.Hommel: Physical Review B, 1998, 58[20], 13619-26