Résumé
Gallium nitride has been grown using low pressure MOCVD and ammonia and triethylgallium as precursors. A wide range of operating conditions have been investigated : the temperature was varied between 950 and 1050 degrees C and the V/III molar ratio was changed from 1000 to 10000. The influence of the growth parameters on the optical quality is reported here. For optimized epilayers, low temperature reflectance data have been taken and analyzed in the context of a multi-polariton model using a non local description of the dielectric constant The energy positions of the resonances have been analyzed in terms of joint contributions of the actual wurtzite structure in the one hand and of residual stress fields in the other hand This enables us to give a relationship between the optical transition energies and the in-plane biaxial stress in the layers.