Kinetics of recombination radiation related to heavy-hole excitons in a GaAs/AlxGa[_,As(x = 0.05) structure with shallow tunneling-isolated quantum wells of 3 and 4 nm width was studied at temperatures 5 - 60 К It was found that the activation energy of the rate of thermal emission of excitons from quantum wells is nearly equal to the sum of electron and heavy-hole localization energies.