Abstract
Photoluminescence (PL) spectra of InGaN/GaN multiple quantum wells excited by ultrafast laser pulses are investigated over broad ranges of excitation levels and temperatures. The PL peak energy undergoes blue, red, zero, and blue shifts with increasing the excitation fluence density. Such a peculiar behavior can be explained based on competing processes of screening of the built-in electric field by the photogenerated carriers, band-gap renormalization, and band-filling effect. We have also measured and analyzed the dependence of the PL energy and linewidth on the temperature. Due to the interplay between the band-gap renormalization and band-filling effect, the PL energy shifts to the highest value, whereas the PL linewidth reaches the minimum value at approximate to 60 K. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775605]