The temperature (T) dependence of the yellow-red photoluminescence ban
d is studied in the range from 300 K to 10 K. From the simultaneous in
tensity and lifetime measurements it is possible to separate unambiguo
usly the radiative and non-radiative components of the decay process.
From the analysis of the non-radiative component a model is suggested
in which potential barriers can confine excitons, limiting in this way
the possible paths for non-radiative recombination.