The di‐interstitial in silicon: Electronic properties and interactions with oxygen and carbon impurity atoms

Abstract

New experimental and theoretical results on the silicon di‐interstitial (I2) and its interactions with oxygen and carbon impurity atoms in Si crystals are reported. Electronic structure calculations indicate that I2 has an acceptor and a donor level in the gap, which are close to the conduction and the valence band edges, respectively. Experimental results, which support the theoretically predicted high mobility of I2, are discussed. It is argued that mobile I2 can be trapped by oxygen and carbon impurities. The I2O center has a donor level at Ev +0.09 eV. Two absorption bands at 936 and 929 cm−1 are assigned to the local vibrational modes of the I2O defect in the neutral and positively charged states, respectively. The binding energy of I2O relative to the separated I2 and Oi species is 0.22 eV. The disappearance of the I2O complex upon thermal annealing occurs in the temperature range 50–100 °C and is accompanied by the introduction of another defect, which gives rise to two hole emission signals from energy levels at Ev +0.54 and Ev +0.45 eV. It is argued that these levels are related to a complex consisting of interstitial carbon and interstitial silicon atoms (CiI). The stable configurations of the CiI pair have been found.