Effects of interface states on the transport properties of all-oxide La0.8Sr0.2CoO3/SrTi0.99Nb0.01O3 p-n heterojunctions

Electrical transport properties of heteroepitaxial p-n junctions made of La0.8Sr0.2CoO3 and SrTi0.99Nb0.01O3 were studied. Junctions display highly rectifying current-voltage characteristics over a wide temperature range (20-300 K). Two distinct transport mechanisms are identified: tunneling assisted by interface states at T< 130 K and diffusion/recombination at higher temperatures. Capacitance-voltage characteristics are used to determine the junction built-in potential at different frequencies. A capacitance relaxation is found due to charge trapping at interface states. Interface states, which deeply affect transport, are discussed in connection to charge-transfer processes related to the polarity mismatch at the interface. (C) 2008 American Institute of Physics.