Gallium contacts on p-type silicon substrates

A significant reduction in contact resistance of palladium/silicon contacts was realised by the use of a thin intermediate gallium layer. The contact resistance of the palladium/gallium/silicon contact was found to be similar to aluminium/silicon contacts on 0.5 Omega cm silicon. Solar cells process ed on 1 Omega cm substrates with this structure demonstrated better contact properties than conventional aluminium/silicon contacts. The improved char acteristics are believed to be a result of gallium/silicon alloying at low temperature (400 degreesC). The palladium layer is critical as aluminium/ g allium/silicon layers show dramatically increased contact resistance. The p alladium silicide may interact with the aluminium layer to form a stable te rnary compound, preventing aluminium from penetrating deeper into the silic on. Copyright (C) 2001 John Wiley & Sons, Ltd.