Ab initiocalculations on the initial stages of GaN and ZnO growth on lattice-matched ScAlMgO₄(0001) substrates

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The initial stages of GaN and ZnO epitaxial growth on lattice-matched ScAlMgO 4 substrates have been investigated by ab initio calculation. The geometrical parameters and electronic structure of ScAlMgO 4 bulk and (0001) surface have been investigated by density-functional first-principles study. The effects of different surface terminations have been examined through surface energy and relaxation calculations. The O–Mg–O termination is more favorable than other terminations by comparing the calculated surface energies. It should be accepted as the appropriate surface structure in subsequent calculation. The initial stages of GaN and ZnO epitaxial growths are discussed based on the adsorption and diffusion of the adatoms on reconstructed ScAlMgO 4 (0001) surface. According to theoretical characterizations, N adatom on the surface is more stable than Ga. O adatom is more favorable than Zn. These observations lead to the formation of GaN and ZnO epilayer and explain experimentally-confirmed in-plane alignment mechanisms of GaN and ZnO on ScAlMgO 4 substrates. Furthermore, the polarity of GaN and ZnO surfaces on ScAlMgO 4 (0001) at the initial growth stage have been explored by ab initio calculation. Theoretical studies indicate that the predominant growths of Ga-polar GaN and Zn-polar ZnO are determined by the initial growth stage.