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 4×10¹⁶ and 6×10¹⁶ cm⁻³ that traps carriers, influencing the determination of the barrier height.