Excitonic absorption above the Mott transition in Si.

We present experimental evidence for the existence of excitonic states above the excitonic Mott transition in both highly doped and highly excited silicon. Previous limitations to resolve the fundamental absorption edge of Si at dense carrier plasmas are overcome employing a novel spatially and time-resolved spectroscopy. We show that the obtained density dependent excess absorption at 75 K represents an excitonic enhancement effect, which is attributed to persisting many-body interactions.