Adhesive properties study on the interfaces of AlN and metal of Pd, Ag and Cu

AlN is used as high power LED package material because of its excellent thermal conductivity. But its poor adhesive with metal is not compatible with the later processing sequence. The properties of the bonding between the deposited palladium, silver, copper and the clean Al-terminated (0001) surface of wurtzite AlN are investigated by using the density-functional theory. The results show that the sites of deposited metal atoms on N site are more stable than that on Al site. Relaxations are found at all the studied interfaces. The bonding energies of Pd/AlN, Ag/AlN and Cu/AlN are respectively 2.75, 1.98, 2.26 eV. Hybridizations of s orbit and p orbit of the deposited metal atoms are observed, which contributes to the bonding energy of interface. The moving to lower energy state of the d orbit and the easier transfer of electrons to semi-empty d orbit in the case of deposited Pd results in the higher bonding energy of Pd/AlN interface.