The co-sputtering of dual ZnO and Ga2O3 targets was used to fabricate a Ga-doped n-type ZnO layers (ZnO:Ga) layers in this work. The performance ZnO : Ga layers were achieved through the substrate heating of 400 oC (Sub:400) and the rapidthermal- annealing (RTA) of 500 oC (RTA : 500). RTA : 500 had a low resistivity of 5.29 × 10−4 Ωcm and its transmittance was nearly over 95% in the visible-wavelength region. For X-ray photoelectron spectroscopy (XPS) spectra of the O 1s core level, two characteristic peaks were observed at Sub : 400 and RTA : 500 layers. One is the chemical bonding of Zn-O and another one is caused by the Ga-O bonds consisting Ga2O3. Whereas, the core level of the P 2p3/2 XPS spectra was appeared to three peaks. The first dominant peak located at 1117.9 eV was attributed to GaZn, which is caused by a Ga3+ ion substituting Zn2+ ion in ZnO lattice. The other two low-intense spectra took the form of the metallic Ga and oxide bonding. Furthermore, the XPS result indicates that the crystal quality of RTA : 500 is superior to that of Sub : 400. From the photoluminescence measurement, RTA : 500 showed excellent optical properties due to the formation of the low lattice defect in the layer. These finding indicate that the post annealing process of the ZnO : Ga layers is responsible for the improvement of the layer quality.

Keywords: Semiconducting II-VI materials, Characterization, Physical vapor deposition processes, Post annealing.