Coulomb-induced nonlinearities in GaN microdisks S. Shojaei, F. Troiani, A. Asgari, M. Kalafi and G. Goldoni Eur. Phys. J. B, 65 4 (2008) 505-509 Published online: 25 September 2008 DOI: 10.1140/epjb/e2008-00357-8