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

Zinc oxide (ZnO) thin film was grown on CaF2 (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 caxis oriented ZnO film was highly transparent and quite smooth. In photoluminescence (PL) spectrum at 10 K, the neutral donor bound exciton (D0X) emission was identified at 3.362 eV (I4), the neutral acceptor bound exciton (A0X) emission at 3.346 eV (I9). Free A- and B-exciton emissions at 3.374 eVand 3.386 eV, respectively, as well as the phonon replicas of free A-exciton and D0X 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/CaF2 film exhibited n-type conduction, with the resistivity of 114 V cm and the Hall mobility of 15.7 cm2/Vs.