Comparative analysis of the carrier dynamics of GaN quantum dot (QD) and GaN quantum well (QW) separated confinement heterostructures (SCHs) with low-Al-content AlGaN waveguide layers is reported. A redshift (blueshift) of QD (wetting layer) emission is found with respect to QW emission, as expected from the thickness hierarchy of these objects. The influence of nonradiative processes on QD emission in QD SCH is dramatically reduced compared to the case of QW SCH. It is concluded that GaN QDs in low-Al-content AlGaN matrix are robust localization centers and that the carrier dynamics is seriously affected by the built-in internal field effect. (c) 2006 American Institute of Physics.