Electronic structure of GaN and AlN surfaces

The electronic structures of GaN and AlN (1 × 1) surfaces are studied by employing an ab initio ´mixed-basis + norm-conserving non-local pseudopotential´ method. Atomic partial densities of states and charge density distribution are calculated and analyzed. Present calculations show that the Ga- and Al- terminated surfaces are more stable than that of the N-terminated. All the (1 × 1) surfaces have strong metallic conductivity. Properties of Al surface growing on wurtize GaN subtract with an in-plane strain are also considered by using first-principle total-energy calculations. With the increasing strain, Al atom demonstrates a tendency occupying the hollow site.