Stability of a planar-defect structure of the wurtzite AlN (10(1)over-bar0) surface: Density functional study

The formation energy of a structure is usually increased by the appearance of a defect. A stoichiometric planar defect structure of the wurtzite AlN (10 (1) over bar0) surface, however, is found to be lower in energy than the ideally truncated surface by first-principles calculations. The intriguing phenomenon is directly attributed to the large scale surface relaxation induced by the defect structure and the intrinsic reason is pointed to the strong ionicity and small c/a (lattice constant ratio) of AlN. A suggested growth mode shows that the defect surface structure is compatible with the growth of the correct wurtzite AlN film on the (10 (1) over bar0) plane.