by the inclusion of nitrogen Y. Miyajima, G. Adamopoulos, S. J. Henley, V. Stolojan, Y. Tison, E. Garcia-Caurel, B. Drévillon, J. M. Shannon, and S. R. P. Silva Nano-Electronic Centre, Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, United Kingdom Laboratoire de Physique des Interfaces et des Couches Minces, UMR 7647 CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France