Defects in cubic silicon carbide (3C-SiC) epilayers, that were grown using different techniques and on different substrates, were studied in terms of electrical activity and device limiting implications. An electrical characterization by conductive atomic force microscopy (C-AFM) showed that stacking faults (SFs) are normally the predominant type of defects that are electrically active at the semiconductor surface and, therefore, the most important defects that can affect the contact properties on these epilayers. It is also shown that an ultraviolet (UV) irradiation process can be used to suppress detrimental leakage currents passing through SFs that are carbon terminated at the semiconductor surface. Indeed, current-voltage characterization of Au/3C-SiC diodes showed a subsequent improvement of the Schottky behavior.