Recombination-enhanced migration of interstitial aluminum in silicon

Abstract

We report the first observation of recombination-enhanced recovery of a defect in silicon which is otherwise normally stable at room temperature. This defect, produced by 1.5-MeV electron irradiation of aluminum-doped material at room temperature, is identified as isolated interstitial aluminum through correlated deep-level transient-capacitance spectroscopy and EPR studies. The recovery rate constant in the absence of minority-carrier injection is 3(${10}^9$) exp(- 1.2±0.1 eV/kT) ${\sec }^{-1\mathrm{}}$. Under saturated injection conditions, it is 70 exp(- 0.27±0.03 eV/kT) ${\sec }^{-1\mathrm{}}$. This represents an enhancement of the recovery rate by a factor of ∼ ${10}^8$ at room temperature. We conclude that this enhancement results from an efficient conversion of the electronic energy available upon carrier capture to local vibrational energy of the defect which assists it over the migration barrier. The second donor level of the defect ($\frac{{\mathrm{Al}}_i^{+}}{{\mathrm{Al}}_i^{++}}$) is determined to be at $E_V+0.17\mathrm{}$ eV. We conclude, however, that the enhancement results from carrier capture and recombination at the first donor level ($\frac{{\mathrm{Al}}_i^0}{{\mathrm{Al}}_i^{+}}$) the position of which has not yet been determined. The implications of these results to the properties of the self-interstitial in silicon are discussed.