Growth and characteristics of ZnO thin film on CaF2 (11-21) substrate by metalorganic vapor phase epitaxy

Abstract Zinc oxide (ZnO) thin film was grown on CaF 2 (11–21) substrate by metalorganic vapor phase epitaxy (MOVPE) and the structure, surface morphology and the opto-electrical properties of the film were investigated. It was found that preferential c -axis oriented ZnO film was highly transparent and quite smooth. In photoluminescence (PL) spectrum at 10 K, the neutral donor bound exciton (D 0 X) emission was identified at 3.362 eV (I 4 ), the neutral acceptor bound exciton (A 0 X) emission at 3.346 eV (I 9 ). Free A- and B-exciton emissions at 3.374 eV and 3.386 eV, respectively, as well as the phonon replicas of free A-exciton and D 0 X were also observed, indicating high optical quality of the ZnO film. Temperature-dependent PL spectra demonstrated that the free exciton emission was dominant at a temperature larger than 215 K. Hall measurement showed that the ZnO/CaF 2 film exhibited n-type conduction, with the resistivity of 114 Ω cm and the Hall mobility of 15.7 cm 2 /Vs.