Temperature- and field-dependent leakage current of epitaxial YMnO3/GaN heterostructure

Epitaxial ferroelectric YMnO3 (YMO) thin films were fabricated on (0001) GaN substrates by pulsed laser deposition followed by rapid thermal annealing. The temperature and field dependence of the leakage current of YMO/GaN interface was studied in a temperature range from 150 to 300 K and for an applied voltage up to 10 V. In a low temperature region from 180 to 220 K, the YMO/GaN interface acted as a Schottky barrier with a height of 0.27 eV for a field below 1.4 MV/cm, while the leakage mechanism was governed by the Fowler-Nordheim tunneling for a field above 1.4 MV/cm. Moreover, a space-charge-limited-current behavior was observed in a high field for a temperature above 270 K, while an Ohmic behavior was observed in a low field. In comparison, the dominant leakage mechanism of In/YMO interface was an Ohmic behavior in the whole measured voltage and temperature ranges.