Epitaxial growth of nonpolar AlN films on ZnO substrates using room temperature grown GaN buffer layers

The authors have grown nonpolar AlN layers on m-plane ZnO substrates using pulsed laser deposition and investigated their structural properties. The direct growth of AlN on ZnO substrates at 750 degrees C results in the formation of polycrystalline materials due to significant interfacial reactions between AlN and ZnO. On the other hand, m-plane AlN was grown epitaxially on the ZnO substrates by using a GaN buffer layer prepared at room temperature (RT). The full width at half maximum value for AlN 1 (1) over bar 00 x-ray rocking curve was determined to be 468 arc sec. Grazing incidence angle x-ray reflectivity measurements revealed that the heterointerface between AlN and RT GaN is quite abrupt. X-ray diffraction measurements revealed that the in-plane epitaxial relationship is < 0001 >(AlN)parallel to < 0001 >(GaN)parallel to < 0001 >(ZnO). These results indicate that the use of the RT GaN buffer layer makes it possible to take full advantage of small lattice mismatches and the wurtzite structure of the ZnO substrates.