GaN on Si offers a promising technology for the low-cost production of wide-bandgap devices. Here, we present approaches towards the growth of GaN on technologically most relevant Si(001) substrates and methods to grow single-crystalline c-axis-oriented GaN on Si(001) with omega-scan FWHMs of 986 arc sec for the (0002) Bragg reflection. Strain is still the major issue for the established growth on Si(111). A study on the generation of strong tensile stress by Si-doping is presented. We find that tensile stress generation is dominantly dependent on the Si doping concentration and the edge dislocation density. (c) 2006 Elsevier B.V. All rights reserved.