We have carried out ab initio self-consistent calculations to investigate the extent to which the band offset can be modified by polar layers. The cases studied are double layers of Ge in bulk GaAs (for which the offsets are totally due to induced dipoles) in (100) and two distinctly different (111) geometries. The (111) double layer with the maximum number of Ge-Ge bonds is found to be energetically the most stable and to have the smallest dipole, but it is still large (0.7 eV) compared to typical band offsets in semiconductors. We argue that this demonstrates the potential possibility of providing a mechanism for band-offset engineering using thin layers at interfaces.