AlxGal-xN-layers are applied in various devices based on group-III-nitride semiconductors. Crystalline quality, composition and morphology need to be controlled by properly adjusting growth processes. Here, we report on AlGaN growth by low-pressure MOVPE on planar and patterened surfaces of sapphire and 6H-SiC(0001) with focus on Al-incorporation and lateral growth. All layers show good surface morphology, near bandedge luminescence and no sign of phase separation (Al-concentration < 50%). The Al-incorporation depends critically on growth parameters. For high pressures of 200 mbar Al is hardly incorporated which can be understood as a result of prereactions involving TMAl and NH3. For patterened substrates PL indicates lateral variation in Al composition as a consequence of mass transport and a reduced lateral growth rate. (C) 2004 Elsevier BN. All rights reserved.