Copper-related deep-level centers in irradiatedp-type silicon

Abstract

Deep-level centers are investigated in the $p$-type Si on copper-contaminated samples which were also electron irradiated. Standard and Laplace-transform deep-level transient spectroscopy techniques were employed to characterize the samples. Several Cu-related centers are observed to form either as a result of the low-temperature Cu diffusion into the irradiated crystals or due to irradiation of the Cu-contaminated samples and subsequent annealing up to 400 ${}^{\ifmmode^\circ\else\textdegree\fi{}}$C. In all crystals, two Cu-related defects are found to be the most abundant; each of them possesses a pair of levels in the lower half of the gap. The Arrhenius signatures for one pair are measured to be practically identical to those for the donor and acceptor levels of substitutional copper Cu${}_{s}$, respectively, the levels of other defect being only barely different from the Cu${}_{s}$ levels. Analysis of the introduction rates and depth profiles of the deep-level centers points to the vacancy--oxygen complex (VO, the A center) as the precursor of the most abundant Cu-related defects. It is inferred that Cu${}_{s}$ is formed in irradiated silicon due to interaction with the VO centers via the rather stable intermediate CuVO complex.