Levels of substitutional copper disturbed by an oxygen atom in n-type silicon

The deep-level spectrum of n-type silicon crystals doped with copper during float-zone growth was investigated using the DLTS and Laplace-DLTS techniques. In addition to the well-known second acceptor of substitutional copper (Cus=), two more bulk levels were observed after preliminary annealing at 350 °C: Cu5 and Cu6 at 0.16 and 0.59 eV below the bottom of the conduction band, respectively. The DLTS signatures of the Cu5 and Cu6 levels were practically identical to those of the ECu−5 and ECu−6 levels found by Markevich et al. in electron-irradiated, Cu-contaminated silicon [Solid State Phenom. 131-133, 363 (2008)]. Considering our and literature data together, we infer that Cu5 and Cu6 are the second and first acceptor levels, respectively, of one defect. Accounting for the similarity of the Cu5 and Cus= levels, we presented experimental evidence showing that the Cu5/Cu6 defect is substitutional copper disturbed by a nearby oxygen atom, {Cus,Oi}. Hydrogen could be another constituent of the Cu5/Cu6 complex because the studied crystals were grown in wet argon atmosphere.