Quantum dot formation in InGaN layers embedded in a GaN matrix is studied as a function of total reactor pressure during low-pressure MOCVD growth. An increasing In content in InGaN layers grown at higher pressures is found, accompanied both by a higher spread of the In distribution inside the layers and a decomposition of the integral luminescence into an ensemble of spectrally sharp emission lines. In contrast, InGaN layers with low In content do not show luminescence properties related to carrier localization in quantum dots. (C) 2004 Elsevier B.V. All rights reserved.