TEMPERATURE-INDUCED DELOCALIZATION OF EXCITATIONS IN GAAS ALAS TYPE-II SUPERLATTICES/

This paper describes investigations of the photoluminescence spectra o f heterostructures containing short-period type-II GaAs/AlAs superlatt ices grown both within the regime where the heterojunction is smoothed , and in a regime where it is not smoothed, in the temperature range 1 0-40 K. A quantitative analysis of the experimental data shows that th e quenching of exciton luninescence in the majority of cases is charac terized by a single value of the activation energy E-2 = 8 +/- 1 meV w hich coincides with the value of the binding energy of an X-Gamma exci ton. It is concluded that the primary reason for quenching in this tem perature interval is thermal dissociation of the exciton into a pair o f free carriers whose delocalization is accompanied by nonradiative re combination at traps. It is observed that smoothing the heterojunction leads to an increase in the probability of quenching by 1-2 orders of magnitude on the average.