Oxygen DX center in In_0.17Al_0.83N: Nonradiative recombination and persistent photoconductivity

Using a hybrid density-functional scheme, we address the O impurity substitutional to N (O_N) in In_0.17Al_0.83N. Our modelling supports In clustering to account for the strong band-gap bowing observed in In_xAl_1−xN alloys. To study the O_N defect in In_0.17Al_0.83N alloys, we therefore consider a model containing an In cluster and find that the most stable configuration shows four In nearest neighbors. We show that such a O_N defect forms a DX center and gives rise to two defect levels at 0.70 and 0.41 eV below the conduction band edge, in good agreement with experiment. The calculated defect energetics entail a fast nonradiative recombination upon photoexcitation at room temperature and account for the observation of persistent photoconductivity at low temperature.