The study of structural defects induced by the introduction of Mg during the growth of MOCVD GaN is presented. The magnesium incorporation into the crystal growth not only induces changes in the stacking sequence from hexagonal to cubic structures, but also inverts the GaN polarity from Ga-face to N-face. Based on the different surface structure and surface migration length of absorbing precursors for each polarity type (Ga- or N-face), the 3D growth on top of the N-face triangular defect is described. The N-face material is characterized by three dangling bonds of nitrogen that point Lip toward the c-plane surface, enhancing the crystal growth along the c-axis. (C) 2002 Elsevier Science Ltd. All rights reserved.