EXCITON AND FREE CARRIER DYNAMICS UNDER CONDITIONS OF IMPURITY PHOTOIONIZATION IN EPITAXIAL GAAS

Experiments are presented in which epitaxial n-GaAs layers were excited by the pulses of two lasers. i) The first pulse creates by interband pumping free carriers by which hole traps are populated. ii) The second pulse of subband excitation excites the crystal some time later after termination of the interband excitation pulse and results in the release of carriers and in the appearance of exciton luminescence. The results show that while holes are localized at deep traps, electrons created during interband excitation remain free in the conduction band and are not captured by impurities.