Bandgap renormalization of ZnO epitaxial thin films

Optical gain spectra in ZnO thin films were observed by pump-probe method. The carrier density in this experiment was estimated to be n=2.7×1019 cm−3 and bandgap energy shift was estimated to be 350 meV from the optical gain spectra. Renormalized bandgap energy was calculated using two theoretical models and was compared with the experimental results. It was found that Beni and Riceʹs model explains the experimental data.