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Three-level system for numerical modeling of ultraviolet and visible photoluminescence of aluminum-doped zinc oxide

The emission properties of aluminum-doped zinc oxide are numerically investigated. A complete model for photoluminescence, based on the set of rate equations for electron–hole recombination, is used to study the influence of carrier concentration (1017–1021  cm−3) on visible and ultraviolet (UV) emission. The set of coupled rate equations is solved numerically using the fourth-order Runge–Kutta technique for various optical pump intensities. The results for low carrier concentration (∼1017  cm−3) show that at low pump intensity (0.01  mJ/cm2), visible emission is dominant in the emission spectrum, and as the pump intensity increases (∼1  mJ/cm2), the UV emission becomes dominant. The study of ultrafast dynamics shows that for pump pulse durations of less than ∼1  ns, the intensity of UV emission is an order of magnitude larger compared to the visible intensity for aluminum-doped zinc oxide samples with carrier concentration ∼1018  cm−3.