Hexagonal AlN (0001) heteroepitaxial growth on cubic diamond (001)

Structural properties of a hexagonal aluminum nitride (AlN) (0001) layer grown on a cubic diamond (001) substrate by metalorganic vapor-phase epitaxy (MOVPE) are investigated to discuss its growth mechanism. It was found that the AlN layer consists of tilted and rotated domains, which are nucleated just on diamond (001) substrates at the initial growth stage. The tilted AlN domains form on the diamond {111} facets of the pits, which are created on the diamond (001) surface during the thermal cleaning in H2. The AlN[0001] direction of the tilted domains is oriented normal to the diamond {111} facets because the atomic bonding configurations of AlN(0001) and diamond (111) planes are similar. On the other hand, two kinds of rotated AlN domains form on the diamond (001) surface. The [0001] direction of the rotated AlN domains is oriented normal to diamond (001) surface, and the AlN[1010] or [1120] direction is oriented to the diamond [110] direction. The formation of the two kinds of rotated AlN domains originates from the nucleation on two different diamond (001) terraces with one atomic layer height difference.