This article investigates the growth of InN layers on (100) InP in ultra-high vacuum using a glow discharge source (GDS). Auger electron spectroscopy (AES) was used to understand the different steps of the nitridation process with the analysis of In-MNN, N-KLL and P-LMM transitions. A modeling of Auger signals using a stacked layers model allows us to confirm that four monolayers of indium nitride are created on (100) InP. InN layers grown on (100) InP were studied optically by photoluminescence (PL) spectroscopy versus the excitation power and the sample temperature (10-300 K). Results show broad spectral band energy close to the lowest reported InN bandgap. The temperature dependence of the PL peak energy showed a S-shaped behavior (decrease-increase-decrease). The results suggest that the InN-related emission is significantly affected by the change in carrier dynamics with increasing temperature: the effect can be due to the large exciton localization effects. (C) 2009 Elsevier B.V. All rights reserved.