Effect of a ZnO buffer layer on structural and electrical properties of ZnO:Al,P thin films grown by RF magnetron sputtering

Structural and electrical properties of ZnO:Al_0.01P_0.04 thin films were investigated with respect to the growth temperature of the ZnO buffer layers deposited by RF magnetron sputtering. The ZnO buffer layers on c-plane sapphires showed three different types of in-plane orientation relationships between ZnO and Al₂O₃ at different growth temperatures: ZnO[101̅0] // Al₂O₃[101̅0] at 200 °C, a mixture of ZnO[101̅0] // Al₂O₃[101̅0] and ZnO[101̅0] // Al₂O₃[112̅0] at 300 °C, and ZnO[101̅0] // Al₂O₃[112̅0] at 600 °C. The in-plane orientation of the ZnO:Al_0.01P_0.04 thin film followed the orientation of the ZnO buffer layer regardless of its growth temperature. The ZnO:Al_0.01P_0.04 film grown on a ZnO buffer layer deposited at 600 °C had a carrier concentration of 1.18 × 10¹⁶ cm⁻³, mobility of 7.16 × 10° cm²/(V s), and resistivity of 7.36 × 10¹ Ω cm, indicating p-type characteristics.