Photoluminescence from Si:Er under front and backside excitation

Photoluminescence (PL) of Si:Er samples was investigated in two experimental configurations, the excitation beam from an argon-laser was applied either from the Er-implanted, or from the opposite side of the sample. In both cases the same PL spectrum, dominated by the so-called ‘cubic’ Er-related center, was observed. Significant differences were found in excitation power dependence, and in kinetics of PL signal measured in the two configurations. The difference in the power dependence indicates energy loss in the bulk of the sample. A pn-junction created in the p-type sample upon Er implantation was considered as a possible origin of the differences observed in kinetics of Er-related photoluminescence. In addition to these effects, a slowly decaying Er-related photoluminescence was observed to appear under backside illumination. It is argued that it might represent the true radiative lifetime of Er ion embedded in silicon crystalline matrix.