Transmission electron microscopy and X-ray diffraction measurements revealed the presence of stacking faults in undoped cubic GaN thin layers. The importance of the defects in the interfacial region of the films was demonstrated by showing that the SFs acted as nucleation sites for precipitates of residual impurities such as C and Si present in the GaN layers grown on SiC(001) substrates. The imaging secondary ion mass spectroscopy technique was used to locate these impurities. The systematic decrease of the stacking fault density as a function of the layer thickness was explained by an annihilation mechanism. Finally, the effects of usual dopants on the structural properties of GaN layers were considered. It was shown that Mg had a tendency to incorporate out of the Ga site by forming Mg precipitates for a concentration higher than 1019/cm3 in contrast with the results found for heavily Si doped layers.

Structural Properties of Undoped and Doped Cubic GaN Grown on SiC (001). E.Martinez-Guerrero, E.Bellet-Amalric, L.Martinet, G.Feuillet, B.Daudin, H.Mariette, P.Holliger, C.Dubois, C.Bru-Chevallier, P.A.Nze, T.Chassagne, G.Ferro, Y.Monteil: Journal of Applied Physics, 2002, 91[8], 4983-7