Influence of Er substitution on the properties of ZnO: A comprehensive study

Abstract

Er-doped ZnO (Zn(1-x)Er(x)O) films with (002) preferential orientated wurtzite structure were fabricated on a c-plane sapphire substrate by pulsed laser deposition (PLD). The effects of Er composition, oxygen pressure during growth, and post-growth annealing on the films' structural, electrical, and optical properties were studied by employing a comprehensive spectroscopic approach. Er-doped ZnO films with a resistivity of 4 × 10−4 Ωcm, electron conductivity n+∼1021 cm−3, and high optical transmittance (>90%) were disclosed to be appropriate candidates for transparent conducting electrode applications. A shallow donor is reported to be associated with the ErZn defect, which is optically inactive. Er-doped ZnO samples grown with high Er composition and oxygen pressure don't show n+ conductivity because of the formation of an O-rich ErZn-related compensating defect. Annealing at 750 °C converts the ErZn shallow donor to another defect configuration, which is optically active for intra-4f-shell transition emissions, but no longer a shallow donor. The growth condition for maximizing the intra-4f-shell transition emission was also obtained.