Discovery of Polyexcitons

We report the first experimental evidence for the existence of free polyexcitons ($n>\mathrm{}2\mathrm{}$) in a semiconductor. Resolved polyexciton lines, together with the biexciton line, were observed in the green photo-luminescence spectrum of ultrahigh-purity silicon. We propose that the unresolved luminescence of these polyexcitons in the "ordinary" near-infrared photoluminescence process may provide an alternative explanation for a band interpreted by others to be due to a new condensed phase of the electron-hole plasma.