Diode Property and Positive Temperature Coefficient of Resistance of Pt/Al2O3/Nb:SrTiO3

The rectification of the Pt/amorphous Al2O3 (a-AO)/Nb-doped SrTiO3 (NSTO) structure with excellent applicability as a selector for crossbar array resistive switching random access memory is introduced. The maximum forward/reverse current ratio exceeds 10(6), and the nonlinearity is also as high as 10(6) at room temperature. The barrier height at the a-AO/NSTO interface is investigated via X-ray photoelectron spectroscopy and is found to be 1.57 eV. The expected conduction mechanism is trap-assisted tunneling in the forward bias condition. The barrier height at the Pt/a-AO interface is examined by fitting the current-voltage results at various temperatures according to the Fowler-Nordheim transport mechanism, under the reverse bias condition, and it is found to be 2.75 eV. Moreover, the temperature dependence measurement of the current-voltage characteristics exhibits the positive temperature coefficient of resistance (PTCR) effect in reverse bias. This PTCR effect can be understood from the electron trapping of the acceptor-like states at the a-AO/NSTO interface with increasing temperature. The involvement of the PTCR effect under the reverse bias condition and the slight increase in the forward current further enhance the diode performance up to 10(7) at 70 degrees C, which is the highly promising performance of the present structure.