Growth and characterization of ZnO thin films on GaN epilayers

Dense ZnO(0001) films formed at 500degreesC via coalescence of islands grown via metalorganic vapor phase epitaxy (MOVPE) either on GaN/AlN/SiC(0001) substrates or on initial, coherent ZnO layers. Conical crystallites formed due to thermal expansion-induced stresses between the ZnO and the substrate. Interfaces between the ZnO films on GaN epilayers exposed either simultaneously to diethylzinc and oxygen or only to diethylzinc at the initiation of growth were sharp and epitaxial. Interfaces formed after the exposure of the GaN to 02 were less coherent, though an interfacial oxide was not observed by cross-sectional transmission electron microscopy (TEM). Threading dislocations and stacking faults were observed in all films.