Photoluminescence dynamics of InGaN/GaN quantum wells with different in concentrations

The photoluminescence (PL) dynamics of InGaN/GaN quantum wells with different In concentrations x(In), have been measured. The PL emission forms a broad band consisting of two parts with dramatically different dynamics. The high energy part (QW(H)) is present only under higher excitation densities (>10(3) W/cm(2)), it has fast decay (of a few tens of ps) and changes only slightly with temperature. Its relative amplitude and the PL lifetime tau increase with the x(In),. The second, low energy part (QW(L)) has slow decay (of the order of 10 ns), its amplitude saturates under higher excitation densities and quickly vanishes when the temperature increases. At 10 K the QWL lifetimes change from tau = 1.8 +/- 0.2 ns x(In), = 0.11 up to 20 +/- 4 ns (x(In) = 0.4) while the thermal activation energy (E-a = 18 +/- 3 meV) is not sensitive for the In concentration. We propose that QWH and QWL come from nonlocalised and localised carrier recombination, respectively.