Photoluminescence Investigations of AlGaN on GaN Epitaxial Films

Abstract

AlGaN on GaN epitaxial films with Al contents between 6% and 76% were investigated by stationary photoluminescence experiments which allows to determine the dependence of the energy gap on alloy composition. The observed increase of the luminescence linewidth as a function of the Al molar fraction can be explained by alloy broadening. The localization energy of the bound exciton increases considerably and reaches a value of 53 meV for 61% Al. It could imply that the donor binding energy would markedly deviate from its effective mass value, an unexpected result if the residual donor is Si.