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

The photoluminescence (PL) dynamics of InGaN/GaN quantum wells with differe nt In concentrations x(In), have been measured. The PL emission forms a bro ad band consisting of two parts with dramatically different dynamics. The h igh 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 s lightly with temperature. Its relative amplitude and the PL lifetime tau in crease 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 de nsities and quickly vanishes when the temperature increases. At 10 K the QW L lifetimes change from tau = 1.8 +/- 0.2 ns x(In), = 0.11 up to 20 +/- 4 n s (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 f rom nonlocalised and localised carrier recombination, respectively.