The defects in InP epitaxial structures (containing in part Pt
nanoparticles) and SiGe/Si heterostructures, and their electrical
behaviour are studied. In InP structures pinholes, in SiGe/Si
structures misfit dislocations were observed in the epitaxial
layers. These defects yielded different anomalies of the electrical
behaviour, as excess and leakage currents, instabilities, anomalous
temperature dependence and anomalous apparent barrier height.
It is shown that inspite of anomalies, the electrical measurements
provide useful and reliable information about the structures.