Microstructural characteristics of AlN thin layers grown on Si(110) substrates by molecular beam epitaxy: Transmission electron microscopy study

The microstructural properties of an aluminum nitride (AlN) layer grown on a silicon (Si(110)) substrate were studied in detail using transmission electron microscope techniques to determine atomic structure and dislocation behavior. AlN islands elongated along the [112¯0]AlN//[1¯10]Si direction were observed at the initial growth stage on the Si(110) substrate. The threading dislocations with a Burgers vector vertical to the interface, most probably be = [0001] of the wurtzite structure, were frequently observed in the AlN thin film. Due to anisotropic biaxial strain distributions, two different atomic structure behaviors were observed along the two in-plane directions; a coherent interface was observed along the [112¯0]AlN//[1¯10]Si direction and a semicoherent interface, including periodic extra-half planes, was observed along the [1¯100]AlN//[001]Si direction. The extra-half planes were observed at approximately two monolayers above the interface, and not at the exact interface.