Abstract
Selected molecular beam epitaxy of zinc blende (111) or wurtzite (0001) GaN films on polar MgO(111) is achieved depending on whether N or Ga is deposited first. The cubic stacking is enabled by nitrogen-induced polar surface stabilization, which yields a metallic surface. High-resolution transmission electron microscopy and density functional theory studies indicate that the atomically abrupt semiconducting interface has a Mg-O-N-Ga stacking, where the N atom is bonded to O at a top site. This specific atomic arrangement at the interface allows the cubic stacking to more effectively screen the substrate and film electric dipole moment than the hexagonal stacking, thus stabilizing the zinc blende phase even though the wurtzite phase is the ground state in the bulk.
- Received 16 December 2004
DOI:https://doi.org/10.1103/PhysRevLett.94.216101
©2005 American Physical Society