ALD growth of ZnO on GaN: Schottky barrier height engineering using ZnO interlayer

Electrical properties of Pt/GaN Schottky diodes have been explored using ZnO interlayers (ILs) grown by thermal atomic layer deposition, which were systematically tuned by varying the growth temperature and thickness of ZnO ILs. For the 20-nm-thick ZnO ILs grown at different temperatures, the growth temperature of 100 °C showed the best rectifying characteristics. The thermionic field emission (TFE) model could explain the forward current characteristics for the growth temperatures of 80, 100 and 150 °C while the tunneling current became dominant for the growth temperature of 200 °C. For the ZnO ILs grown at 100 °C with different thicknesses, the barrier height decreased first and then increased with increasing the ZnO thickness. The samples revealing high interface state density showed the strong tunneling current. It is inferred from the result that both growth temperature and thickness of ZnO IL can be modulated to achieve good Schottky or ohmic contacts for GaN based devices.