Influence of the substrate on the photo-luminescence dynamics in GaInN epilayers

We present results of temperature-dependent, time-resolved photoluminescence (PL) measurements on a set of Ga1−xInxN (x≅0.08) layers grown at the same conditions on three different substrates: bulk (high pressure grown) GaN, SiC and Al2O3. At 9 K, the maximum of the PL occurs at about 3.1 eV. The linewidths are 48, 80 and 90 meV for the layers grown on GaN, Al2O3 and SiC, respectively. The smallest width suggests the highest homogeneity of the GaInN/GaN. The PL lifetimes (about 0.8 ns) and intensities are similar in all three samples. The spectral diffusion of the PL (shift of the PL peak energy with time) is thermally activated. The highest shift (ΔE=90 meV) and an activation energy Ea=80 meV are observed in the GaInN/SiC sample, the lowest (ΔE<3 meV) in the GaInN/GaN sample. The smallest ΔE (interpreted as a conduction and valence band fluctuation amplitude) found in the layer grown on GaN is due to the low dislocation concentration resulting from the good lattice matching.