Effects Of Temperature On Intra-Band Photoluminescence In Zinc Oxide (Zno) Semiconductor

Abstract

In this research work, the theoretical description of the photoluminescence in Zinc Oxide semiconductor due to the intra-band and band to band transition of free carriers is performed. First, the excitation of free carriers from the valence band to conduction band and from different localized state to the conduction band by the illumination of sufficient energy is considered. Then, the radiative recombination rates of photo-generated carriers from the conduction band to different energy levels within the forbidden gap, from the conduction band to the valence band and from different energy levels within the band gap to the valence band are described in detail. A theoretical model for minority carrier trapping is also investigated to explain the dependence of the photoluminescence on the trap energy. By using illumination, and net rate of recombination, the intensity of light emitted during recombination of free carriers is determined by assuming one incident photon ejects one electron at a time. Finally, variation of photoluminescence intensities along with localized state energy and transition energy is considered at different temperatures. The obtained results show that, for the variation of photoluminescence intensities with transition energy, at very low temperature, there is no recombination taking place between the conduction band and the localized state; and between the localized states and the valence band. As temperature increases the photoluminescence due to the transition of free electrons from the conduction band to the valence band,𝐼𝐶𝑉, from the conduction band to the localized states,𝐼𝐶𝑇 and from the localized states to the valence band,𝐼𝑇𝑉 are increasing.