Electrical characteristics of palladium Schottky contacts to hydrogen peroxide treated hydrothermally grown ZnO

The formation of Schottky barrier contacts to hydrogen peroxide treated ZnO has been investigated. Low resistivity hydrothermally grown single crystal ZnO wafers of n-type were used. Pd contacts deposited on organic solvent cleaned O face (000 (1) over tilde) showed Ohmic behavior, while on the H2O2 treated O face up to nine orders of magnitude in rectification of the current was obtained for biases of -2 and +2 V. Concurrently, the surface roughness increases from 1.0 +/- 0.5 up to 2.0 +/- 0.5 nm due to the H2O2 treatment. A majority of the contacs deposited were stable or improved their performance by annealing in air at 200 degrees C for 30 min. However, the contacts both before and after the annealing exhibited ideality factors of at least similar to 1.8 at +0.5 V suggesting that the current transport cannot be described as purely thermionic. Finally, results of capacitance versus voltage and capacitance versus temperature measurements are discussed and show a dominant electron state at similar to 0.32 eV below the conduction band edge.