Ferroelectric Pb(Zr,Ti)O3/Al2O3/4H–SiC diode structures

Abstract

$\mathrm{Pb}(\mathrm{Zr,Ti}){\mathrm{O}}_3$ (PZT) films (450 nm thick) were grown on 4H–silicon carbide (SiC) substrates by a pulsed-laser deposition technique. X-ray diffraction confirms single PZT phase without a preferred orientation. Stable capacitance–voltage $\mathrm{(C–V)}$ loops with low conductance $\text{(<0.1\hspace{0.17em}}{\mathrm{mS/cm}}^2,$ $\tan \text{\hspace{0.05em}δ∼0.0007}$ at 400 kHz) and memory window as wide as 10 V were obtained when 5-nm-thick ${\mathrm{Al}}_2{\mathrm{O}}_3$ was used as a high band gap ${\mathrm{(E}}_g\text{∼9\hspace{0.17em}}\mathrm{eV})$ barrier buffer layer between PZT ${\mathrm{(E}}_g\text{∼3.5\hspace{0.17em}}\mathrm{eV})$ and SiC ${\mathrm{(E}}_g\text{∼3.2\hspace{0.17em}}\mathrm{eV}\mathrm{).}$ High-frequency (400 kHz) $\mathrm{C–V}$ characteristics revealed clear accumulation, and depletion behavior. Although the charge injection from SiC is the dominant mechanism for $\mathrm{C–V}$ hysteresis in ${\mathrm{PZT/Al}}_2{\mathrm{O}}_3/\mathrm{SiC},$ negligible sweep rate dependence and negligible applied bias dependence were observed compared to that of PZT/SiC. By using room-temperature photoilluminated $\mathrm{C–V}$ measurements, the interface states as well as the charge trapping in the ${\mathrm{PZT/Al}}_2{\mathrm{O}}_3$ stacks have been calculated.