Emission mechanism of localized deep levels in BeZnO layers grown by hybrid beam method

BeZnO layers, which are new materials for ultraviolet-light-emitting devices, were grown by hybrid beam method. The mobility and the carrier concentration on the Be _x Zn_1−x O layers of x = 0.28 were confirmed to be 2.83 cm²/V s and 4.16 × 10¹⁸ cm⁻³, respectively. Also, the optical properties attributed to the thermal quenching phenomenon of BeZnO were analyzed by photoluminescence as a function of temperature. With increasing temperature, the intensities and the spectral widths on the localized deep-level emissions of 3.6230 eV exponentially reduced and tended to broaden, respectively. Therefore, the temperature dependences of the full width at half maximum and the intensity were explained in terms of a configuration coordinate model. The broad emissions of 3.6230 eV without any fine structure were acted by a strong electron-phonon coupling due to the interaction between the radical beryllium and the ZnO host lattice. In addition, the Frank-Condon shift was found out to be 78.9 meV with the associated phonon energy of 15 meV. Thus, the activation energy of the nonradiative emission participating in the thermal quenching process was estimated to be 48.6 meV. Consequently, its value corresponds to the thermal dissociation energy requiring for the recombination of the conduction electron from the exciting state to the ground state.