Identification of compositionally invariant deep levels introduced by plastic strain in epitaxial Ge0.30Si0.70 and deformed bulk Si

Presented is a demonstration of a strong correlation between strain-relaxation related hole traps in p-type Ge0.30Si0.70 and hole traps previously reported in bulk p-type plastically deformed (PD) Si. This suggests that plastic strain introduces characteristic deep electronic states in the GexSi1-x band gap, irrespective of the deformation process and composition, at least within the range 0&lex&le0.30. With changing composition in the GexSi1-x alloy system, the deep level transient spectroscopy determined activation energies track changes in valence band energy, indicating that these characteristic deep levels are fixed in energy relative to some reference level such as the vacuum energy level or perhaps some average of the band structure. This result implies that the observed deep levels have the same structural origin in relaxed Ge0.30Si0.70 epitaxial layers and in bulk PD Si, and that these structural defects are unlikely to be extrinsic in nature.