Effect of oxygen on exciton transitions in silicon

Abstract

The spectral line shape of the α 1 no-phonon line of the exciton bound to phosphorus donors in silicon is asymmetric and it broadens rapidly with increasing oxygen concentration. We show that these effects can be accounted for by assuming that a neutral oxygen atom has a short-range potential, decreasing sufficiently rapidly with distance that the first-order effect on the exciton energy level is proportional to the exciton density on the oxygen atom. Different combinations of oxygen atoms around the phosphorous centers produce a variety of frequency shifts resulting in the inhomogeneous broadening of the α 1 line. Assuming that oxygen atoms are randomly distributed relative to the phosphorus donors, the profile of the α 1 line can be simulated and the strength of the short-range potential determined.