Journal of Crystal Growth 298 (2007) 186–189 Systematic theoretical investigations of compositional inhomogeneity in In x Ga 1x N thin films on GaN(0 0 0 1) Tomonori Ito à , Shingo Inahama, Toru Akiyama, Kohji Nakamura Department of Physics Engineering, Mie University, 1577 Kurima-Machiya, Tsu 514-8507, Japan Available online 13 November 2006 Abstract We systematically investigate the compositional inhomogeneity near surface, interface, and dislocation in In x Ga 1x N thin films on GaN(0 0 0 1) by using our empirical interatomic potential and the Monte Carlo (MC) method. The compositional inhomogeneity is discussed by evaluating individual contribution such as strain relief at the surface and the interface between In x Ga 1x N and GaN with/ without misfit dislocations. The empirical potential calculations reveal that the dislocation core energy for bulk InN (1.51 eV) is smaller than that of GaN (1.81 eV). This suggests that In atoms preferentially reside in the lattice sites near the dislocation core in In x Ga 1x N. The MC simulation clarifies that In surface segregation is found in In x Ga 1x N thin films pseudomorphically grown on GaN(0 0 0 1), where the surface composition of In is greater than that of bulk In composition because of strain relief and bond energy profit of In atoms at the surface. Further MC simulation for the system including both surface and misfit dislocations implies that the In atoms segregate at the surface strongly while In atoms segregate near the misfit dislocations weakly. r 2006 Elsevier B.V. All rights reserved. PACS: 68.35.Dv; 81.05.Ea; 81.10.Aj Keywords: A1. Defects; A1. Interfaces; A1. Surfaces; B1. Nitrides 1. Introduction GaN-based III–V compound semiconductors are attrac- tive materials for short-wavelength light-emitting diodes and laser diodes. In particular, In x Ga 1x N is expected to cover the full region of visible light through careful control of the Ga/In ratio from GaN to InN. However, homo- geneous In x Ga 1x N thin films with a large In mole fraction is difficult to grow because of the compositional unstable nature. Furthermore, In segregation in In x Ga 1x N has been often found at the surface or interface during epitaxial growth including MOVPE [1,2]. Although there have been some theoretical studies for these inhomogeneities, most of the studies focuse on the compositional inhomogeneity in In x Ga 1x N without dislocations [3–5]. In general, the difference in lattice parameter and thermal expansion coefficients between the In x Ga 1x N and the substrate induces a high density of threading and misfit dislocations (MDs) in the grown In x Ga 1x N thin films. Thus, compositional inhomogeneity in In x Ga 1x N thin films should be clarified by considering the contribution of dislocations in addition to those of surface and interface. To this end, we calculate the dislocation core energies for various core structures in GaN and InN by using the empirical interatomic potential. Based on the results, we systematically investigate the compositional inhomogeneity in In x Ga 1x N thin films on GaN(0 0 0 1) using the Monte Carlo (MC) method, where we employ the model structure with/without stable five and seven coordinated channels (5/7) core MD network at the interface. The origin of the compositional inhomogeneity is discussed by evaluating individual contribution such as energy profit of bond species at the surface and strain relief due to lattice constraint and dislocation formation at the interface. ARTICLE IN PRESS www.elsevier.com/locate/jcrysgro 0022-0248/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2006.10.015 à Corresponding author. Tel./fax: +81 59 231 9724. E-mail address: tom@phen.mie-u.ac.jp (T. Ito).