Method for shallow impurity characterization in ultrapure silicon using photoluminescence

The advantages of very low excitation density photoluminescence for the quantitative determination of shallow impurity concentrations in ultrapure Si are demonstrated using the weakly-absorbed 1047 nm output of a Nd:YLF laser. Compared to the usual high excitation method, which uses an argon ion laser, the weak bound exciton luminescence is significantly enhanced relative to that of the free exciton, and competing luminescence from multiexcitonic species, which complicates the accurate determination of the bound exciton intensities, is eliminated. Also, the presence of the laser Raman line in the same spectral region as the luminescence allows for the accurate determination of relative luminescence quantum efficiencies and can reveal the presence of deep traps. Finally, we report calibrations for boron, phosphorus, and arsenic in the concentration range 1011 to 1015 cm−3.