Leakage current suppression and breakdown voltage enhancement in GaN-on-GaN vertical Schottky barrier diodes enabled by oxidized platinum as Schottky contact metal

In this work, the oxidized metal PtOx was employed as the Schottky contact metal in the fabrication of gallium nitride (GaN)-on-GaN vertical Schottky barrier diodes (SBDs). Compared with the GaN SBD with just Pt Schottky anode, the Pt/PtOx/Pt-GaN SBDs exhibited a substantial reduction in reverse leakage current density (J(R)) from 5.2 x 10(-6) A cm(-2) to 5.6 x 10(-9) A cm(-2) (@ -50 V) and a large rise in the breakdown voltage (V-BD) from 152 to 368 V, as well as maintaining the similar on-state characteristics in terms of turn-on voltage and on resistance. The temperature-dependent current-voltage characteristics of the fabricated devices further revealed that the Pt/PtOx/Pt-GaN SBDs possessed a higher Schottky barrier height and better high-temperature stability. Such an improvement should be attributed to the electric dipole effect in the PtOx layer. Moreover, the additional thin Pt layer between PtOx and GaN almost have no influence on the electric dipole effect of PtOx but can effectively protect the GaN surface from plasma damage and oxidation during the PtOx deposition. We believe that the proposed Pt/PtOx/Pt-GaN Schottky contact scheme provides a straightforward and effective strategy to develop next-generation GaN power electronic devices.