Structural and electronic characterization of GaN on MgAl2O4 (111) substrates

We report the structural and electronic characterization of GaN on magnesium aluminate (MgAl2O4) (111) substrates using first‐principles calculations. Atomic structures and surface energies of eight stoichiometric MgAl2O4 (111) surfaces with different terminations are investigated after surface relaxations. The results of surface energy indicate that the Al (Mg)‐termination is relatively more energetically stable than other terminations. The initial stage of growth is studied based on adsorption of the Ga or N atoms on the optimized MgAl2O4 (111) surface. The results of adsorption energy reveal that N atoms are more stable than Ga atoms on the surface. The bonding characteristics of the GaO and NO adsorption bonds are examined by the COHP technique, which confirms the strong bonding interactions between N atom and the surface. The first atomic layer for GaN growth should be a nitrogen layer. It leads to the experimentally‐confirmed epitaxial relationships for GaN/MgAl2O4. Additionally, the polarity determination of GaN on MgAl2O4 (111) is also studied based on adsorption of Ga atom on the nitrogen layer covered MgAl2O4 surface. The results indicate that Ga atom preferentially adsorbs at the central site among three N atoms on the surface, which leads to the formation of Ga‐polar GaN.