Phonon Replica Dynamics in High Quality GaN Epilayers and AlGaN/GaN Quantum Wells

We present an experimental study of the exciton and phonon replica dynamics in high quality GaN epilayers and AlGaN/GaN quantum wells (QW) by means of picosecond time-resolved photoluminescence (PL) measurements. A non-exponential decay is observed both at the zero phonon line (ZPL) and at the n = 1 LO replica. Time-resolved spectra unambiguously assign the replica to the free exciton A recombination. Optical migration effects are detected both in the epilayer and the QWs samples and disappear as the temperature increases up to 60–90 K. Even though the sample quality is comparable to state-of-the-art samples, localization effects dominate the exciton dynamics at low temperature in the studied GaN based strucures.