Electronic properties of iron-boron pairs in crystalline silicon by temperature- and injection-level-dependent lifetime measurements

Iron-boron pairs in crystalline silicon are studied by measuring the recombination lifetime as a function of injection density, doping concentration, and temperature. The characteristic crossover point of the injection-level-dependent carrier lifetime curves measured before and after optical dissociation of the iron-boron pairs is analyzed to determine the energy level as well as the electron- and hole-capture cross sections of the acceptor level of iron-boron pairs, assuming known recombination parameters for interstitial iron. The doping concentration dependence of the crossover point gives an electron-capture cross section of (1.4±0.2) × 10-14 cm2, while the temperature dependence results in a hole-capture cross section in the range from 0.5× 10-15 to 2.5× 10-15 cm2 and an energy level of (0.26±0.02) eV below the conduction-band edge.