Edge dislocation effect on optical properties in wurtzite ZnO

The effect of edge dislocations on optical properties in wurtzite ZnO is studied using a k·p multiband Hamiltonian model. An edge dislocation is modeled as a negatively charged line due to its electron-acceptor nature with an elastic strain field due to the lattice distortion around the dislocation. The electrostatic potential strength of the negatively charged dislocation depends on the filling fraction, which describes the fraction of acceptor sites occupied by trapped electrons along the dislocation line. To understand the effect of electrostatic potential strength, the filling fraction has been varied in this work. Using the calculated energy levels and wave functions for electrons and holes from the k·p multiband Hamiltonian, the spontaneous emission spectrum has been obtained as a function of dislocation density and filling fraction. The calculated results are compared with available experimental photoluminescence data. The band edge peak intensity decreases significantly with increasing dislocation density. It is found that the electrostatic potential strength does not affect the band edge peak emission, but it generates deep level emissions. For low filling fractions, corresponding to high temperature, the most commonly observed green luminescence is found. For a high filling fraction, corresponding to low temperature, the green luminescence shifts to red luminescence, which is consistent with experimental observation.

► We study effects of dislocations on optical property in ZnO.
► We exam effect of dislocation density and filling fraction.
► Band edge peak intensity decreases with increasing dislocation density.
► ZnO is less sensitive to dislocations than GaN.