Extended defects in semiconductors can trap charge and lead to changes in carrier concentration and mobility. Here we consider the trapping effects of pores, microcracks, and dislocations in GaN and SiC, as analyzed by deep level transient spectroscopy (DLTS), transmission electron microscopy (TEM), and scanning surface potential microscopy (SSPM). The defect structures are modeled as spheres, plates, and cylinders for pores, cracks, and dislocations, respectively, and their potentials are directly compared with those measured by holographic TEM and SSPV. The dynamics of the capture and emission processes are investigated by DLTS, although the standard DLTS analysis framework is not applicable here and must be replaced by a more general formalism. As an example, 40-nm-dia. nanopores in SiC can each hold more than 100 electrons, and they exhibit anomalous capture and emission properties. (c) 2005 WILEY-VCH Verlag GmbH E Co. KGaA, Weinheim.