Adsorption properties of Al, Ga, and N related particles on GaN substrate surface by first principle calculations

Abstract

GaN is promising for fabricating high-quality substrate for growth of AlN and AlGaN film. To study the microscopic adsorption and bonding mechanism of AlN and AlGaN film growth on GaN substrate, the first principle calculations are applied to study the adsorption Al atom, Ga atom, N atom, AlN molecules, and GaN molecules on GaN substrate. The adsorption energies, adsorption states, bonding properties, electronic local functions, and density of states are analyzed. The results reveal that N atom has the lowest adsorption energy and the strongest capacity among above five adsorption particles. And the top side of N atom on GaN substrate surface is the favorable adsorption site for all particles. Moreover, the adsorbed Al atom, Ga atom, N atom, AlN molecules, and GaN molecules all form chemical bonds with substrate atoms. The adsorbed Al atom, Ga atom, and N atom all form a covalent bond connection with the atoms in GaN substrate while the AlN molecules and GaN molecules are connected by an ionic bond with GaN substrate. Furthermore, the total density of state distribution and band gap of GaN substrate have change after adsorption of particles, which further verified that the chemical adsorption occurred after the adsorption of the above particles. The density of states of AlN molecule with Al atom closer to GaN substrate and GaN molecule Ga atom closer to GaN substrate on GaN surface match the most with GaN substrate,indicating that the lattice matches well when AlN molecule with Al atom closer to GaN substrate and GaN molecule Ga atom closer to GaN substrate adsorbed on GaN substrate.