Comparison of Anodic Etching to Chemical Etching and EBIC

The results obtained with anodic etching depend on the current density used. For small current densities there is a tendency to reveal only electronically active defects, whereas at higher current densities all defects are etched. This can be seen in comparison with "normal" chemical etching and with EBIC
Comparison anodic etching -EBIC

The pictures show the same area of a solar Si sample (always repolished after one experiment):
a) Anodically etched at small current density. Only some of the twin boundaries at the lower half of the picture are faintly delineated.
b) Anodically etched at high current density. The twin boundaries at the lower half of the picture are delineated.
b) Chemically etched. The twin boundaries are partially delineated.
c) EBIC Micrograph. Upon close inspection, it is mostly compatible with a).
This gives the impression that anodic etching at small current densities reveals only electronically active defects whereas at higher current densities it shows all defects. This can be clearly demonstrated in another optimized comparison below
comparison anodic etching -EBIC
Left, the etching structure obtained at small, on the right with high current densities. The EBIC picture is shown in the middle. It is obvious that only a few twin boundaries show up at low current densities and in the EBIC mode.
One more example confirms this result
Low current density
High current densitiy

With frame With frame as PDF

go to 6.1.1 Observation of Dislocations and Other Defects

go to Principle of Electron Beam Induced Current Microscopy

© H. Föll (Defects - Script)