Recombination dynamics of localized excitons in In0.20Ga0.80N-In0.05Ga0.95 multiple quantum wells

Dynamical behavior of radiative recombination has been assessed in the In0.20Ca0.80N (2.5 nm)/ In0.05Ga0.95N (6.0 nm) multiple-quantum-well structure by means of transmittance, electroreflectance (ER), photoluminescence excitation (PLE), and time-resolved photoluminescence (TRPL) spectroscopy. The PL at 20 K was mainly composed of two emission bands whose peaks are located at 2.920 eV and 3.155 eV. Although the peak at 3.155 eV was weak under low photoexcitation, it grew superlinearly with increasing excitation intensity. The ER and PLE revealed that the transition at 3.155 eV is due to the excitons at quantized levels between n = 1 conduction and n = 1 A(Gamma(9 upsilon)) valence bands, while the main PL peak at 2.920 eV is attributed to the excitons localized at the trap centers within the well. The TRPL features were well understood as the effect of localization where photogenerated excitons are transferred from the n = 1 band to the localized centers, and then are localized further to the tail state.