Characterization of PN junctions of doped Mott insulators

A heterojunction comprising a La1.9Sr0.1CuO4 thin film on a 0.5 wt. % Nb doped SrTiO3 single-crystal substrate was fabricated using magnetron sputtering deposition and ion milling etching techniques. Rectification has been observed in the current–voltage characteristics of the heterojunctions from 30 to 300 K. The temperature evolution of the ideality factor implies the important role of barrier inhomogeneity at the junction interface. A systematic study of capacitance as a function of frequency under different bias voltages at room temperature was also carried out. The capacitance can be explained by deep-level defects in the space charge region.