Collateral evidence for an excellent radiative performance of Al _xGa_1-xN alloy films of high AlN mole fractions

Recombination dynamics for the deep-ultraviolet (DUV) near-band-edge emission of Al_xGa_1-xN epilayers of high AlN mole fractions (x) are studied using time-resolved spectroscopy. Their low-temperature radiative lifetime (_R) is longer than that for the epilayers of low-x Al_xGa_1-xN, AlN, or GaN due to the contribution of bound and localized tail-states. However, _R shows little change with temperature rise, and the value is a few ns at 300 K. The results essentially indicate an excellent radiative performance of Al _xGa_1-xN alloys of high x, although the luminescence efficiency of Al_xGa_1-xN DUV light-emitting-diodes reported so far is limited by the short nonradiative lifetime.