  Experimental evidence indicating the beneficial impact of a phosphorous
diffusion gettering (PDG) in the reduction of trapping centers is shown, as
observed by means of inductively coupled photoconductance (PC) decay and
lifetime measurements carried out on upgraded metallurgical-grade silicon
(UMG-Si) wafers. The presence of trapping species dominating the long time
range of the PC decay of UMG material (slow traps), which is effectively
removed after a PDG conducted at 780 Celsius, is detected. Notwithstanding, a
second trapping mechanism, characterized by a shorter time constant, still
governs the response at very low injection levels after the gettering.
Furthermore, the beneficial effect of the PDG is studied as a function of
processing time, showing minority carrier bulk lifetime improvements up to
18-fold, up to the range of 70 us. Thereby, the way for developing gettering
strategies capable of successfully removing trap centers and improving the bulk
lifetime of unconventional Si material is paved.

Applied Physics;Materials Science