Propagating optical phonons and their properties in GaN/AlN quantum wells W. D. Huang, Y. J. Ren, J. F. Yan, Q. Wu and S. H. Zhang Eur. Phys. J. Appl. Phys., 54 1 (2011) 11301 Published online: 13 April 2011 DOI: 10.1051/epjap/2010100340