It was noted that 2 shallow hole traps dominated deep-level transient spectroscopic data from strain-relaxed Si0.7Ge0.3 layers which had been grown onto (100) Si by means of ultra-high vacuum chemical vapor deposition at temperatures of up to 560C. The trap energy levels were at Ev + 0.06 and Ev + 0.14eV, and the trap concentrations were up to 5 x 1014/cm3 in relaxed layers with threading dislocation densities ranging from 2 x 107 to 4 x 107/cm2. A logarithmic dependence of the filling rate indicated that these traps were associated with extended defects. They were absent from dislocation-free samples. The annealing temperature of the deep-level transient spectroscopy peaks was consistent with the assumption that these traps were related to defect complexes at dislocations, rather than to intrinsic dislocation states or to isolated defect complexes. The trap concentrations were proportional to the O concentration in the film; thus suggesting that O was a constituent of the defect complex.

P.M.Mooney, L.Tilly, C.P.D'Emic, J.O.Chu, F.Cardone, F.K.LeGoues, B.S.Meyerson: Journal of Applied Physics, 1997, 82[2], 688-95