Characterization of interface defects in BiFeO₃ metal–oxide–semiconductor capacitors deposited by radio frequency magnetron sputtering

In this work, we study the structural and electrical properties of BiFeO₃ MOS capacitors with a special focus on the oxide–semiconductor interface for gate dielectric applications. For this purpose BiFeO₃ thin films with a thickness of 300 nm were deposited on p-type Si (100) substrates at 0 °C by RF sputtering. Half of the films were annealed at 550 °C for 30 min in atmospheric environment while the other half were kept as-deposited. XRD and SEM measurements were performed for both samples for structural characterization. MOS capacitors were fabricated by evaporation technique using Al from samples. For electrical characterizations of MOS capacitors, capacitance–voltage (C–V), conductance–frequency (G_p/ω–F) and leakage current density–voltage (J–V) measurements were performed. The XRD analyses show that BiFeO₃ thin films are polycrystalline with some impurity phases, which influence the electronic device properties. The formation of crystallization is confirmed by SEM measurements. Debye length, barrier height and flat band voltages showed variations due to the frequency dependent charges, partially originating from interface defects, in the device structure. Therefore ignoring effects of frequency dependent charges can lead to significant errors in the analysis of electrical characteristics of MOS capacitors. Moreover, the obtained results from analyses of C–V, G_p/ω–F and J–V characteristics of annealed samples depict that all measured and calculated parameters are of the same order for novel MOS devices. Hence, the BiFeO₃ dielectric layer in fabricated MOS devices exhibits a stable insulation property for gate dielectric applications.