Electrical properties of deep silver- and iron-related centres in silicon

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Abstract
Deep-level defects related to silver and iron in n- and p-type silicon have been investigated using deep-level transient capacitance spectroscopy. In n-type silicon, a silver-related electron trapping state at Ec-0.54 eV was observed, whilst in p-type silicon a hole-trapping state at Ev+0.29 eV was dominant, in agreement with values previously assigned to acceptor and donor states respectively. In iron-diffused silicon, a hole-trapping level at Ev+0.32 eV was observed in the p-type samples. All of these defects were passivated by reaction with atomic hydrogen, and concentration profiles for the two silver-related centres were measured as functions of the temperature of the exposure to the hydrogen plasma. Gamma irradiation produced an additional silver-related hole-trapping level at Ev+0.48 eV, and an iron-related hole-trapping level at Ev+0.39 eV in p-type samples. Both of these centres have been observed in doped samples quenched from 1175 degrees C. Finally, the room-temperature motion of the silver-related hole-trapping (donor) centre (Ev+0.29 eV) under the influence of the electric field in reverse-biased junction diodes is reported. An estimate for the mobility of 2*10-14 cm2 V-1 s-1 at 25 degrees C was obtained for the centres associated with this level.