Optical and x-ray diffraction studies on the incorporation of carbon as a dopant in cubic GaN - Fernandez, J R L; Cerdeira, F; Meneses, E A; Brasil, M J S P; Soares, J A N; Santos, A M; Noriega, O C; Leite, J. R.; As, D J; Köhler, U; Potthast, S; Pacheco Salazar, D G (Physical Review B, 2003)