Luminescence dynamics in GaAs/AlAs superlattices near the type-I/type-II crossover

We report on the time-resolved luminescence of a GaAs/AlAs superlattice with slight type-II band alignment. We show that the inhomogeneous broadening of the type-I transition and the weak type-II oscillator strength load to a dominant luminescence of localized type-I states. We observe a strong increase of the luminescence decay time with increasing temperature and excitation density, which is attributed to the type-II states acting as an electron reservoir.