Electronic properties of defects introduced in strained, epitaxial p-type SiGe alloys during sputter etching in an argon plasma
We have used deep-level transient spectroscopy in an investigation of the electronic properties of defects introduced in boron-doped, strained p-type Si1-xGex alloys with x = 0 and 0.05, during argon plasma sputter etching. These defects are compared with those introduced during electron beam deposition of metal contacts and after 5.4 MeV particle irradiation. Four defects with discrete energy levels, ranging from 0.22 eV to 0.55 eV above the valence band, were introduced in p-Si during sputtering. The most prominent defect, detected in Ar plasma etched samples, has similar electronic properties to those of the defects detected after electron and particle irradiation. The main defects detected in p-Si were also observed in p-Si0.95Ge0.05. One of the dominating peaks has been correlated with the interstitial carbon-interstitial oxygen pair. The decrease in activation energy of this defect with increasing Ge content from x = 0 to 0.05 is found to follow the same variation as the bandgap of strained Si1-xGex/Si. The energy level position of the defect, relative to the conduction band, is therefore the same for x = 0 and 0.05 indicating that such a level is pinned to the conduction band.