EXCITONIC RECOMBINATION OF DEGENERATE 2-DIMENSIONAL ELECTRONS WITH LOCALIZED PHOTOEXCITED HOLES IN A SINGLE-HETEROJUNCTION QUANTUM-WELL

We report the observation of the excitonic recombination of degenerate quasi-two-dimensional electrons with localized photoexcited holes. Lo w-temperature photoluminescence and magnetophotoluminescence spectra e xhibit a well resolved Mahan exciton resonance which is sensitive to e lectron density n(s). We observe a sharp decrease in the exciton oscil lator strength and linewidth with the concomitant formation of biexcit ons and a large discontinuity in the exciton ground-state energy at n( s) almost-equal-to 1.9 x 10(11) cm-2 . An abrupt transition from excit onic to free-electron-localized-hole recombination occurs at n(s) almo st-equal-to 2.2 x 10(11) cm-2.