Well width dependence of disorder effects on the optical properties of AlGaN/GaN quantum wells

We report on a temperature-dependent photoluminescence study of disorder effects on the optical properties of Al0.2Ga0.8N/GaN multiple quantum wells as a function of the well width. It is found that the disorder-induced inhomogeneous broadening of the excitonic density of states increases with decreasing well width. A nonmonotonic temperature variation of the photoluminescence peak energy is observed, and interpreted as a crossover from a thermal to a nonthermal (trapped) distribution of recombining excitons amongst the band-tail states. The luminescence is quenched by two thermally activated mechanisms, and the dependence of the activation energies with well width is accounted for. (C) 2004 American Institute,of Physics.