Type I to type II transition at the interface between random and ordered domains of AlxGa1-xN alloys

We analyze the optical and transport consequences of the existence of ordered and random domains in partially ordered samples of AlxGa1-xN alloys. Using atomistic empirical pseudopotential simulations, we find that the band alignment between random and ordered domains changes from type I to type II at xsimilar or equal to0.4. This leads to an increase by two to three orders of magnitude in the radiative lifetime of the electron-hole recombination. This can explain the experimentally observed mobility-lifetime product behaviors with changing Al concentration. The type I to type II transition results from a competition between the ordering-induced band folding effect and hole confinement on Ga-rich monolayers within the ordered structure. (C) 2004 American Institute of Physics.