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ZnO films (5 nm and 20 nm) have been grown on GaN single-crystal substrates by thermal atomic layer deposition (ALD) and the electrical properties of n-GaN Schottky contacts modified by such ultrathin ZnO films have been characterized. Compared with 5-nm-thick ZnO, 20-nm-thick ZnO exhibited a better rectifying nature. The average barrier height and ideality factor at room temperature were extracted to be 0.64 eV and 2.33 eV, and 1.01 eV and 1.16 eV, for 5-nm-and 20-nm-thick ZnO, respectively. These results indicate that both the barrier height and ideality factor were altered effectively by changing the ZnO thickness. The temperature-dependent reverse currentvoltage (I-V) characteristics revealed that tunneling was dominant for the 5nm-thick ZnO. A laterally inhomogeneous barrier was appropriate to explain the forward I-V characteristics for both samples. Based on the parallel conductance method and forward I-V data, a lower interface state density was observed for 20-nm-thick ZnO, implying improved interface quality. These results suggest that the electrical properties of n-GaN Schottky contacts could be easily modulated by changing the ZnO thickness.

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Modification of interface properties in Pt/n-InP Schottky contacts with atomic layer deposited ZnO interlayer (IL) (5 and 10 nm) has been carried out and the electrical properties were investigated using current-voltage (I-V) and capacitance-voltage (C-V) techniques. The insertion of ZnO IL in the Pt/n-InP interface reduced the effective barrier height. The barrier heights from C-V method were higher with respect to those from I-V method. The interface state density for 5 nm thick ZnO was higher than that for 10 nm thick ZnO. The barrier heights according to thermionic field emission model showed much closer to those from C-V method. Surface passivation and interfacial dipole were suggested to modulate the Schottky barrier at the Pt/ZnO/n-InP interface.

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