We compared InGaN- and AlInGaN-layers grown by metal-organic vapor phase epitaxy (MOVPE) in terms of morphology, growth mode and indium incorporation. The growth parameters of the AlInGaN layers only differed from InGaN growth by an additional trimethylaluminum (TMAI) now. Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) measurements showed that the indium incorporation in AlInGaN was significantly increased compared to InGaN. Atomic force microscopy (AFM) was used to analyze the morphology and the growth mode. The additional T MAI now changed the growth mode from a step-now mode to a 2-dimensional (2D) island nucleation mode, yielding a smoother layer morphology. This behavior can be explained by the low surface mobility of the Al adatoms and their nucleation on terraces between adjacent steps. Step bunching - as observed for InGaN - was avoided during AlInGaN growth. This reduced the AFM root mean square roughness by 40% compared to InGaN. Possible impacts on charge carrier localization in QWs are discussed. (C) 2014 Elsevier B.V. All rights reserved.