In this work we show how in situ measurements of wafer curvature helps for monitoring the strain relaxation in group-III-nitride layers grown by molecular beam eptixay on silicon. In particular, we show the efficiency of GaN/AlN interlayers for growing high quality AlGaN/GaN heterostructures with residual stress that largely compensates the one appearing upon cooling down to room temperature. (c) 2006 Elsevier B.V. All rights reserved.