Inductively coupled plasma (ICP) etching of germanium introduces a single defect, the E0.31 electron trap, for a
large range of argon partial pressures from 4 × 10-3 to 6.5 × 10-4mbar that correspond to ion energies of 8 to 60
eV. Ge of three crystallographic orientations, (100), (110) and (111), treated with 20 and 60 eV ICP had defect
concentration profiles that were similar in appearance, with a maximum concentration of 1014 cm-3 extending
more than a μm into the material, approximately three orders of magnitude deeper than what TRIM simulations
predicted. All profiles were measured using Laplace deep level transient spectroscopy (L-DLTS), a technique
that is sensitive to defect concentrations as low as 1011 cm-3. Isochronal annealing of samples showed
concentration curves broadening after a 400 K anneal and decreasing to the 1013 cm-3 level after a 450 K anneal.
Unannealed samples measured after a year exhibited similar decreases in defect concentration without
broadening of their profiles. A 550 K anneal lowered the defect concentration to levels below the L-DLTS
detection limit. Thereafter additional plasma treatment of the surface failed to reintroduce this defect indicating
that the structure required for the formation of E0.31 was no longer present in the region under observation.