Exciton absorption in silicon at low electric fields

This paper reports for the first time high-resolution transverse EA spectra of Si in low electric fields at liquid-helium temperature. The data conclusively demonstrate that the observed effect is related to the discrete levels of the Wannier exciton and that for the n = 1 level it can be accounted for both qualitatively and quantitatively by means of a Stark approximation where field-induced broadening is phenomenologicaly introduced to allow for weak tunneling-like contributions. The exciton energy levels determined here are in good agreement with the results of wavelength-modulation spectroscopy and all the other parameters of the absorption process are consistent with previous absolute absorption experiments.