Probing of polarization reversal and charge conduction in epitaxial (Ga,Fe)$_{2}$O$_{3}$ thin films on conducting oxide SrRuO$_{3}$

Ga$_{2-x}$Fe$_{x}$O$_{3}$ (GFO) thin films are the promising room-temperature multiferroics since their magnetic T$_{C}$ has been reported up to 370 K at x=1.4. However, most polarization hysteresis loops of the GFO thin films have been showed lossy behaviors due to the large leakage current. The origin probably lies on charge movement between Fe$^{3+}$ and Fe$^{2+}$ sites which is generated by oxygen vacancy. We report the large reduced leakage current of the GFO thin films by chemical doping to reduce Fe$^{2+}$. The doped GFO thin films were deposited by pulsed laser deposition at 750$^{\circ}$C for 15 min in oxygen partial pressure of 200 mTorr on SrRuO$_{3}$/SrTiO$_{3}$ substrates with various doping concentration. Epitaxy of b-axis orientation in out-of plane was confirmed by x-ray diffraction. The leakage current was reduced up to 5$\sim $6 order of magnitude depending on doping concentration. In order to investigate their conduction mechanism, temperature dependent macroscopic I-V curves were measured. Ferroelectric polarization and switching of the films were acquired over a wide range of temperature as well. Scanning probe microscopy has been used to measure local leakage currents as well as polarization reversal as a mode of conductive atomic force microscopy and piezoelectric microscopy, respectively. Local investigation of their electrical properties alludes to ferroelectricity in GFO.