Temperature-dependent capacitance studies of palladium/zinc oxide Schottky diodes

Palladium Schottky contacts were prepared on ZnO films that were deposited by MOCVD on GaAs substrates. We characterize the Schottky contacts by means of current-voltage measurements at different temperatures and demonstrate the advantage of using highly conductive GaAs as a substrate. The capacitance of the Schottky diodes was studied at temperatures between 295 and 360 K. Our measurements reveal that the capacitance of the Schottky diode not only depends on the temperature itself but also on the rate at which the temperature of the sample changes. We discuss diffusion, the pyroelectricity of ZnO and the temperature-dependent hydrogen sensitivity of the Pd/ZnO system as possible explanations for this behaviour.