Influence of Al doping on crystal structure, optical, and photoluminescence characteristics of ZnGa2O4 films

Al-doped ZnGa2O4 (ZAGO) thin film phosphors were grown on the c-plane sapphire substrates by co-sputtering of ceramic ZnGa2O4 (ZGO) and metallic Al targets with the Al concentration in the range of 0-5.35%. A sys-tematic investigation on the effects of Al dopant contents on the crystal structure and optical characteristics of ZAGO films has been conducted. First principle calculations were performed to investigate the preferable site of Al atoms in ZAGO supercell in detail. The high-crystalline nature of 1.65% ZAGO film was evidenced by X-ray diffraction patterns and transmission electron microscopy. Al doping revealed the enhanced bandgap of 5.32 eV for ZAGO films. The X-ray photoelectron spectroscopy was utilized in order to determine the chemical states as well as the stoichiometric Zn/Ga ratio in the ZAGO films. The crystallinity, optical, and photoluminescence (PL) characteristics of the ZAGO films are found strongly influenced by Al doping, O/(Zn + Ga + Al), and Zn/Ga ratio. The PL spectra exhibited the broad bands expanding from 380 to 600 nm with the peak located at 525 nm. The improved PL characteristics of ZAGO phosphors with trace Al (1.65%) demonstrate the promise of a relatively new semiconductor material system ZAGO for high-crystalline thin film phosphors.

Automated summary

Al-doped ZnGa2O4 thin film phosphors were grown on sapphire substrates, and the effects of Al doping on the crystal structure and optical characteristics of the films were investigated.