Exciton freeze-out and thermally activated relaxation at local potential fluctuations in thick Al _xGa _1-xN layers

The Al _xGa _1-xN layers with 0.05≤x≤0.25 were discussed using spectrally and time resolved cathodoluminescence. An s-shaped temperature dependence characterisitc of disordered systems was exhibited by the near-band-edge peak emission energy. The shift in the luminescence peak position with respect to the usual temperature dependence of the band gap was quantified. Analysis shows that at elevated temperatures, when the excitons were delocalized, the decay was significantly faster.