Thermodynamic modeling of native defects in ZnO

ZnO is an important optical material and is an ideal candidate for light emitting diode applications. The optical property of ZnO is determined by its native defects. In this study, the concentrations of native defects and carriers in ZnO are investigated by a four sublattice point defect thermodynamic model. The intrinsic carrier concentration calculated by this model showed a good consistency with the estimation from Maxwell-Boltzmann function. This demonstrates the feasibility of this model. The concentrations of native defects, zinc vacancy, oxygen vacancy and zinc interstitial, are calculated as a function of temperature under different growth conditions such as zinc-rich and oxygen-rich. The calculation results show that ZnO is an intrinsic n-type material and has a slight zinc excess at the congruent melting point due to oxygen vacancies. This model provides a methodology to obtain the information of defect and dopant chemistry in ZnO from a quantitative thermodynamic analysis.