TRANSMISSION ELECTRON-MICROSCOPIC OBSERVATION OF ALN ALPHA-AL2O3 HETEROEPITAXIAL INTERFACE WITH INITIAL-NITRIDING AIN LAYER/

The AlN/alpha-Al2O3 heteroepitaxial interface is investigated using a transmission electron microscope. The epitaxial AlN film is deposited by metalorganic chemical vapor deposition with and without initial nit riding. The initial nitriding method is to convert the alpha-Al2O3 sub strate surface to a nanometer-thick AlN single-crystal buffer layer in NH3 ambient just before AlN deposition. The (1 ($) over bar 210)AlN/( 1 ($) over bar 102) alpha-Al2O3 interface with initial nitriding is fo und to be atomically flat, and no dislocation inside the postdeposited AIN is observed. We have confirmed that initial nitriding is excellen t in improving the crystal quality of the AlN epitaxial layer.