Carbon-doped InAlAs layers grown below-pressure metalorganic vapor phase epitaxy are investigated as a function of growth temperature. Photoluminescence spectra show a significant drop in peak intensity as the growth temperature is reduced due to the incorporation of non-radiative defects. It is shown that the C-doping is not related to the deterioration of the optical properties of the layers. On the other hand both the atomic and the net hole concentration increase as the growth temperature is reduced due to a more efficient C-incorporation. C-related deep donors are also incorporated in the layers. Annealing the samples improve their electrical activity but does not affect the Optical properties. (C) 2002 Elsevier Science B.V. All rights reserved.