Electrical characteristics of lead-free Mn-doped BiFeO₃–SrTiO₃ thin films deposited on silicon substrate using pulsed laser deposition

Lead-free 0.4(BiFe_0.995Mn_0.005O₃)–0.6(SrTiO₃) thin films were deposited on boron-doped silicon (p-Si) through pulsed laser deposition. The effect of different deposition pressures ranging from 4.66 × 10^{− 5} to 13.33 Pa was evaluated, with a corresponding deposition temperature of 700 °C. A conventional lithography process was used to define vertical metal–insulator–metal structures, and the electrical characteristics of these structures were evaluated. The results revealed that as the densification is improved, the leakage current is enhanced and the dielectric constant decreased with the decrease in thickness and increase in deposition pressure. The curve of the current density as a function of the applied electric field exhibited a rectifying effect, with a difference of nearly two orders of magnitude in the current with a forward bias compared to that with a reverse bias. The leakage current mechanisms in metal–ferroelectric–semiconductor structures were investigated as well. The main electrode-limited conduction mechanisms were Schottky emission and Fowler–Nordheim tunneling; the bulk-limited mechanisms were ohmic conduction under low applied electric fields and space charge-limited conduction (SCLC) under high electric fields. The SCLC model was used to calculate the total trap-state density (N_t) at room temperature; N_t was higher in the films deposited under higher pressures.