IMPACT IONIZATION OF FREE AND BOUND EXCITONS IN ALGAAS GAAS QUANTUM-WELLS/

We present a study of the effect of a parallel electric field on the e xcitonic photoluminescence (PL) from AlGaAs/n-GaAs quantum wells (QWS) . We observe sharp thresholds in the quenching of luminescence from fr ee and bound excitons at fields near a few tens of V cm-1. PL lifetime measurements of the excitons show that the recombination lifetime is unaffected during the quenching. The mechanism responsible for the obs erved effects will be shown to be due to impact ionization of the exci tons by the free carriers heated in the electric field.