Size- and doping-dependent time-resolved photoluminescence of doped Si nanocrystals

Time-resolved photoluminescence (PL) has been studied for B- and Sb-doped Si nanocrystals (NCs) fabricated by ion beam sputtering and annealing. For B-doped Si NCs, the PL intensity as well as the PL lifetime (τPL) increases as NC size (d) varies from 1.5 to 2.6 nm, similar to the case for undoped Si NCs, but with further increase of d, they decrease, possibly resulting from the increase of optically less active NCs with the increase of NCs containing more dopants. The PL intensity and τPL monotonically decrease with increasing doping concentration (nD), irrespective of doping element. Si NCs show smaller τPL in B doping than in Sb doping over the full range of nD. The sharp decrease in PL intensity, accompanied by the gradual decrease in τPL for the higher nD of Sb, may be attributed to Auger recombination due to the presence of Sb inside Si NCs. The higher PL quench rate by Sb compared to B could be attributed to better ionization of Sb dopants in Si NCs.