Characterization and ellipsometric investigation of high-quality ZnO and ZnO(Ga2O3) thin alloys by reactive electron-beam co-evaporation technique

High-quality ZnO(Ga2O3) thin films have been co-evaporated by reactive electron-beam evaporation in an oxygen environment. The effect of Ga2O3 on the structural and optical properties has been investigated. X-ray diffraction (XRD) measurements have shown that the ZnO(Ga2O3) alloys are c-axis-oriented. The alloy containing 28% of Ga2O3 showed the best crystallinity. Photoluminescence on ZnO(28%Ga2O3) reveals an enhancement of the ultraviolet near band edge emission at 380 nm while the intensity of the deep-level emissions weakens. A reduction of the oxygen vacancies as well as the reduction of the zinc interstitials with gallium may explain this effect. Thus, the possibility of transitions of electron in the conduction band to a deep acceptor level due to zinc interstitials may decrease. Finally, ellipsometric measurements show that the optimum weight concentration of gallium oxide in the alloys is 28%, thus correlating with the XRD and photoluminescence measurements.