An investigation was made of the nature of the defects and hetero-interfaces in ZnO films which had been grown onto (00•1) sapphire. High-quality epitaxial films were deposited by using pulsed lasers at temperatures ranging from 750 to 800C. The epitaxial relationship of the film with respect to the (00•1) substrate was found to be: (00•1)ZnO||(00•1)sapphire; with the in-plane orientational relationship: [01•0]ZnO||[¯12•0]sapphire. The latter relationship corresponded to a 30º rotation of the ZnO basal planes with respect to the sapphire substrate. This was similar to the epitaxial growth characteristics of AlN and GaN on sapphire. The threading dislocations in ZnO were found to have mainly 1/3<11•0> Burgers vectors. The planar defects, which were mainly I1 stacking faults, were found to lie in the basal plane and had a density of about 105/cm. Epitaxial AlN films were grown at a temperature of about 770C by using a ZnO/sapphire heterostructure as a substrate. This resulted in the formation of a thin reacted layer at the AlN/ZnO interface. These results had implications with regard to low defect contents in ZnO films, as compared to III-V nitrides, and to the use of ZnO films as buffer layers for III-V nitrides.

J.Narayan, K.Dovidenko, A.K.Sharma, S.Oktyabrsky: Journal of Applied Physics, 1998, 84[5], 2597-601