Recombination dynamics of localized biexcitons in AlGaN ternary alloys

摘要

Excitonic optical properties of Ga-rich Al_xGa_(1-x)N ternary alloy epitaxial layers are reviewed on the basis of our recent experimental observations. Photoluminescence due to radiative recombination of biexcitons was clearly observed from the ternary alloys with different aluminum compositions (x=0.019 ～ 0.15). Recombination dynamics of excitons and biexcitons was studied by means of time-resolved photoluminescence spectroscopy. The effect of localization due to alloy disorder on biexcitons was also studied by means of photoluminescence excitation spectroscopy. A Stokes shift of biexcitons was defined experimentally on the basis of two-photon absorption of biexcitons in order to evaluate the degree of biexciton localization quantitatively. A binding energy of biexcitons was determined as a function of aluminum composition. The biexciton localization due to alloy disorder resulted in a strong enhancement of the biexciton binding energy.