Non-cryogenic infrared absorption spectroscopy for direct boron-hydrogen pair quantification

Abstract

Infrared absorption spectroscopy (FT-IR) done at room temperature can be successfully used for the quantification of boron-hydrogen pairs in crystalline silicon in the 1014 to 1015 cm-3 range, where the detection limit is found to be in the low 1014 range. If the fraction of hydrogen that pairs with boron is known, it can be used to draw conclusions about the total hydrogen content in c-Si. Several measurements over the course of formation and dissociation of boron-hydrogen pairs can be obtained comparatively easily due to the lower effort at room temperature. Unlike other methods aiming for the unspecific change in net doping apparently caused by the formation of BH-pairs, the analysis of local vibrational mode (LVM) excitation is highly specific and allows to distinguish between BH-pair formation and other effects impacting hole concentration. Besides the analysis of LVM excitation, the interaction of infrared light with the free electron plasma (Drude’s model) allows for a quantification of hole concentration as well, and thus allows for a direct cross-check with the LVM analysis.