Radiation-induced defect states in low to moderately boron-doped silicon

Low to moderately boron-doped silicon crystals were irradiated at room temperature with a 2.0-MeV electron beam and studied by means of deep-level transient spectroscopy. New dominant hole traps H(0.12) and H(0.07) located, respectively, at 0.12 and 0.07 eV above the valence band, and an electron trap E(0.59) located at 0.59 eV below the conduction band are reported. The states H(0.12), produced directly after irradiation, and H(0.07), formed following 400 °C annealing, are observed in samples of low boron contents (∼10 ¹⁴ cm^-3). The state E(0.59), on the other hand, is observed after 400 °C annealing in the moderately boron-doped samples (∼10¹⁵ cm^-3). Based on the thermal stability and energy position of these states tentative defect identifications are proposed by correlation with published data. Other previously reported hole traps are observed at 0.22 and 0.34 eV above the valence band and are ascribed to the divacancy V₂ (0/+) and the carbon interstitial-carbon substitutional pair, respectively.