The dependence of barrier height on temperature for Pd Schottky contacts on ZnO

Temperature dependent current–voltage ( I– V) and capacitance–voltage ( C– V) measurements have been performed on Pd/ZnO Schottky barrier diodes in the range 60–300 K. The room temperature values for the zero bias barrier height from the I– V measurements ( Φ I–V ) was found to be 0.52 eV and from the C–V measurements ( Φ C–V ) as 3.83 eV. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature, a trend that disagrees with the negative temperature coefficient for semiconductor material. The C–V barrier height decreases with temperature, a trend that is in agreement with the negative temperature coefficient of semiconductor material. This has enabled us to fit two curves in two regions (60–120 K and 140–300 K). We have attributed this behaviour to a defect observed by DLTS with energy level 0.31 eV below the conduction band and defect concentration of between 4×10 16 and 6×10 16 cm −3 that traps carriers, influencing the determination of the barrier height.