Absorption, emission, and carrier dynamics study of MOCVD-grown Al(x)Ga(1-x)N alloys

Optical absorption, emission, and carrier recombination characteristics of AlxGa1-xN epilayers (x = 0.17 and 0.33) were systematically studied by means of transmission, photoluminescence (PL), and time-resolved PL spectroscopy, respectively. A typical energy-gap shrinkage behavior with temperature was observed for both AlxGa1-xN epilayers by absorption measurements, but all anomalous PL temperature dependence was observed: (i) a decrease-increase-decrease behavior of the PL peak energy and (ii) an increase-decrease-increase behavior of the spectral width with increasing temperature. We observed that the effective lifetime was enhanced in the temperature region showing the anomalous temperature-induced emission behavior, reflecting superior luminescence efficiency by suppressing non-radiative processes. The anomalous temperature-induced emission shift is attributed to energy tail states due to alloy potential inhomogeneities in the AlxGa1-xN epilayers with large Al content.