Formation of Titanium Nitride on the GaN(0001) Surface: A Density Functional Theory Study

We have carried out density functional theory (DFT) calculations to study the role of titanium impurity atoms during gallium nitride (GaN) growth. Adsorption and incorporation of Ti atoms on GaN(0001) surface is examined and it is shown that Ti atoms preferentially adsorb at the T-4 sites at low and high coverage. In addition, calculating the formation energy of multiple-impurity configurations, we constructed a surface phase diagram showing the energetically most stable structures as a function of Ti and Ga chemical potentials. Based on these, we find that incorporation of Ti atoms in the Ga-substitutional site is energetically more favorable compared with the Ti surface adsorption on the top layers. This effect leads to the formation of an interfacial crystalline titanium nitride (TiN) compound on the GaN(0001) surface, which can offer a good interfacial combination between Ti and GaN substrates. (C) 2013 The Japan Society of Applied Physics