Recombination activity of iron-gallium and iron-indium pairs in silicon

The recombination activity of iron-gallium (FeGa) and iron-indium (FeIn) pairs in crystalline silicon is studied by means of injection-dependent carrier lifetime measurements on Fe-implanted, Ga- and In-doped p -type silicon wafers of different resistivities (0.3-15 Ωcm). Compared to FeB pairs, FeGa and FeIn pairs are found to be much more effective recombination centers in p -type silicon. Using Shockley-Read-Hall statistics we determine the energy level Et of the FeGa-related center to be 0.20 eV above the valence-band edge E _ν. The strong recombination activity of FeGa is assigned to its large electron-capture cross section σ _n of 4× 10-14 cm2. The hole-capture cross section σ _p is 2× 10-14 cm2. For the FeIn-related recombination center, our measurements show that Et = E _ν +0.15 eV, σ _n =3.5× 10-13 cm2, and σ _p =1.5× 10-14 cm2. Strong illumination with white light is found to dissociate both types of pairs. Storage of the samples in the dark leads to a full repairing of FeGa and FeIn pairs. Lifetime changes measured before and after illumination can be used to determine the interstitial iron concentration in Ga- and In-doped silicon using calibration factors determined from the measured defect parameters.