Photoluminescence from highly excited AlN epitaxial layers

Excitonic optical properties of AlN epitaxial layers have been studied by means of photoluminescence and optical reflectance spectroscopies. The binding energy of free excitons was estimated to be 57meV on the basis of the energy separation between the n=1 ground and n=2 excited states. In addition, the luminescence line due to radiative recombination of biexcitons was observed under high density excitation. The energy separation between free-exciton luminescence and biexciton luminescence was 19meV, which corresponded to the binding energy of biexcitons. Therefore, the ratio of the biexciton binding energy to the exciton binding energy was approximately 0.33.