Generation rate of point defects in silicon irradiated by MeV ions

Abstract

N-type Si samples have been implanted at room temperature wit low doses of 11B, 12C, 16O, 28Si and 74Ge ions. Energies in the MeV range were used, and deep level transient spectroscopy (DLTS) was applied for sample analysis. Irrespective of ion and material type the DLTS spectra are dominated by three levels at ∼ 0.18, ∼ 0.23 and ∼ 0.43 eV below the conduction band edge ( E c ). The concentration of these levels has been determined as a function of ion dose and sample depth. The generation rate of the E c −0.43 eV level exhibits a close proportionality with the elastic energy deposition rate for the different ions while strong deviations from such a dependence are found for the E c −0.23 eV level. Furthermore, evidence is obtained for a substantial surface-enhanced annihilation of migrating monovacancies; for “shallow” defect distributions (peak position ∼ 1 μM) the measured depth profiles profnarrower in shape towards the surface than simulated vacancy profiles while the opposite trend holds for deep distributions (peak position ∼ μM).