TEM observation of nanopipes in heteroepitaxial GaN E. Jezierska, J. L. Weyher, M. Rudzinski and J. Borysiuk Eur. Phys. J. Appl. Phys., 27 1-3 (2004) 255-258 Published online: 15 July 2004 DOI: 10.1051/epjap:2004061