GaN has been grown on Si(110) substrates by metalorganic vapor phase epitaxy using a low-temperature AIN nucleation layer. The atomic arrangement at the AlN/substrate interface has been investigated by high-resolution transmission electron microscopy. Lattice images of the AlN/Si Interface taken along the 〈11 2̄0〉AlN // 〈 11̄0〉 Si and 〈11̄00〉AlN // 〈001 〉Si projections show an abrupt crystalline interface. A highly coherent epitaxial relationship between (1̄00)AlN and (001) Si planes Is observed. The atomic bonding configuration at the AIN/SI interface is analyzed taking into consideration the chemical coordination, lattice mismatch, and net charge balance. A structure model of the bonding at the interface is presented. © 2008 The Japan Society of Applied Physics.