In an attempt to complete the determination of the atomic structure of the {11 (2) over bar 0} planar defects which are found systematically in the interfacial area of (2H) GaN-AlN/6H-SiC, high resolution electron microscopy and atomistic calculations were used and an adequate model was chosen. It is found that the atomic structure corresponds to the ideal 1/2[1 (1) over bar 01]{11 (2) over bar 0} stacking fault model, with no volume expansion.