Mixed-Mode Excitons in the Photoluminescence of Zinc Oxide-Reabsorption and Exciton Diffusion

The photoluminescence of mixed-mode excitons in ZnO at 77 °K has been measured normal to the surface at various angles of the wave vector with respect to the c--> axis. It is shown that the mixed-mode A (n=1) exciton-emission band is strongly influenced by reabsorption, and the exciton diffusion length is estimated to be 0.20 μ. The damping was found to be independent of the angle and was determined to be approximately ℏΓ=2.8 meV.