Fabrication and characterization of nanocrystalline ZnO film-based heterojunction diodes on 4H-SiC

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 [11.2̄0]∥4H-SiC [11.2̄0], which is attributed to the small lattice mismatch of ZnO with 4H-SiC (∼5.5%). The ZnO films with nanosized 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.