Fabrication and Characterization of Nanocrystalline ZnO Film-Based Heterojunction Diodes on 4H-SiC

Abstract

Nanocrystalline n-ZnO/p-4H-SiC heterojunction diodes were successfully fabricated and characterized. The epitaxially grown ZnO films were obtained by using a pulsed laser deposition (PLD) method. X-ray diffraction (XRD) pole figure analysis showed that the c-oriented ZnO films were grown on 4H-SiC (0001) substrates with in-plane orientation of ZnO [11 (2) over bar0]parallel to 4H-SiC [11 (2) over bar0], which is attributed to the small lattice mismatch of ZnO with 4H-SiC (similar to 5.5%). The ZnO films with nano-sized grains were confirmed by surface morphology analysis. In order to investigate the electrical properties, the Ohmic contact electrodes were formed directly onto the ZnO and 4H-SiC surfaces. Current-voltage characteristics of the heterojunction diodes had a good rectifying behavior with an on/off ratio above 10(8). The current transport mechanisms in different bias regions were also discussed.