Unusual intensity dependence of rise and decay timesof free exciton photoluminescence in high purity GaAsand AlGaAs alloys

摘要

Rise up and decay dynamics in high purity GaAs and directgapAlGaAs alloys were studied. In contrast to the previous results boththe rise and decay times of the free exciton PL line show strongly nonmonotonicbehaviors with increasing in excitation power. Sharp increaseof these times with the pulse power increasing from 0.02 pJ to 0.1 pJ is aresult of the change in exciton formation mechanisms from geminate tobimolecular. The decrease in rise and decay times at high excitationpowers can be due to a decrease of the exciton lifetime due to Auger-likeprocesses.