Localized and delocalized states in GaNAs studied by microphotoluminescence and photoreflectance

Optical transitions in GaNAs bulk layer containing 2.2% N have been studied with microphotoluminescence (μ-PL) and photoreflectance. At low temperatures and low excitation conditions, the μ-PL spectra showed sharp PL lines of 100–300μeV widths about 10–20meV below the energy gap. Those lines were attributed to the recombination of localized excitons trapped at local potential minima. When the excitation power was increased, an additional smooth PL band appeared at the higher-energy side. This band corresponds to the light-hole transition in photoreflectance spectrum, i.e., transition between the delocalized states.