Enhancement of activation energies of sharp photoluminescence lines for GaInNAs quantum wells due to quantum confinement

It is shown that localized emission from GaInNAs quantum wells (QW) is composed of sharp photoluminescence (PL) lines. Spectral position of these PL lines varies in a very broad range (similar to 150 meV) but the activation energy of each line is the same within the experimental uncertainty and equals similar to 11 meV. This value is higher than in bulk GaInNAs (similar to 6 meV) and corresponds very well to electron-hole attraction in GaInNAs QW. It means that the source of these sharp PL lines are excitons localized on deep centres, which can recombine radiatively while the thermal energy is smaller than the Coulomb attraction between electrons and holes. Because of this the localized emission composing of sharp PL lines is observed at low temperatures and quenched much faster for GaInNAs layers than GaInNAs/GaAs QWs.