Argon plasma sputter etching induced defect levels in strained, epitaxial p-type Si-Ge alloys

Abstract

Argon plasma sputter etching-induced electronic defects in boron doped, strained p-type Si 1−xGe x alloys with x = 0 and 0.05 have been investigated by deep level transient spectroscopy (DLTS). Four defects with discrete energy levels, ranging from 0,22–0.55 eV above the valence band, were introduced in p-Si during sputtering. These defects are compared to those introduced during electron beam deposition (EB), alpha particle irradiation and Ar ion beam etching. The most prominent defects in Ar plasma etched samples have similar efectronic properties as a defects detected after electron beam, Ar ion beam etching and alpha particle irradiation. The main defects detected in p-Si was also observed in p-Si 0.95Ge 0.05. One of the dominating peaks has been correlated to the interstitial carbon-interstitial oxygen pair. The decrease in activation energy of this defect for increasing Ge-content from x = 0–0.05 followed the same variation as the band gap in Si 1−xGe x/Si. Its energy level position relative to the conduction band is therefore the same for x = 0 and 0.05 indicating that it is pinned to the conduction band. Defect concentration depth profiling revealed that the main defect introduced during argon plasma sputtering and Ar ion beam etching is located very close to the surface and is deeper than that detected after EB deposition.