Electronic structure analysis of threading screw dislocations in 4H–SiC using electron holography

Off-axis electron holography has been used to map the electrostatic potential distribution of threading screw dislocations in differently n-doped 4H–SiC epitaxial layers. Observed phase contrast indicated the presence of a negatively charged dislocation core. Comparison between experimental and simulated potential profiles indicated that the density of trapped charges increased for a higher doped epilayer. Assuming a single level of the trap at the core, the ionization energy of the trap was calculated to be 0.89±0.22 eV.