Optical property and Stokes’ shift of Zn1−xCdxO thin films depending on Cd content

Ternary Zn1−xCdxO films were grown on (0001) sapphire substrates by pulsed laser deposition. The energy band gap of Zn1−xCdxO films decreases with increasing Cd content. An increase of Cd content also leads to the emission broadening, absorption edge broadening, and crystallinity degradation. The absorption edge and ultraviolet emission energy shift to lower energy from 3.357eVto3.295eV and 3.338eVto3.157eV, respectively, with increasing Cd content from 0.3% to 3% at 4K. The Stokes’ shift between the absorption and emission is observed and that indicates the increase of exciton localization with Cd content.