Analysis of Impurity-related Radiative Transitions in Silicon Materials using Temperature-dependent Photoluminescence

The contradictory reports in the literature about the stability of Ga-doped silicon (Si) material for photovoltaic applications, in comparison to those doped with B, necessitate a more detailed understanding of the characteristics of this material before solid conclusions about degradation mechanisms can be made. In this work, high-resolution low-temperature photoluminescence (PL) has been used to investigate and analyze the luminescence from Ga-doped and P+Ga co-doped Czochralski-grown silicon (Cz-Si) materials. Comparison of thermally induced changes in luminescence features for these materials are compared to those occurring in B-doped and P+B co-doped Si materials. It has been found that the Ga bound exciton (BE) exhibits a triplet luminescence structure which is preserved in the co-doped material, explained by the splitting of the exciton ground state. A similar effect does not occur for the BE-related PL signal in B-doped silicon material. A low temperature (10-20 K) range was then used to investigate the temperature-induced changes in impurity related photon emission lines in the PL spectra of the studied materials. The effect of thermal energy on the PL intensity of different radiative recombination channels is elucidated. It has been argued that the presence of compensating impurities causes enhanced radiative recombination of some excitonic emissions while others behave in a similar way as in a single-doped material. The possible relationship of the observed effects on electron-hole recombination at room temperature is discussed.