Formation mechanism of cerium oxide-doped indium oxide/Ag Ohmic contacts on p-type GaN

The authors report on the formation of cerium oxide-doped indium oxide (2.5 nm) Ag (250 nm) contacts to p-GaN. The contacts become Ohmic with a specific contact resistance of 3.42× 10-4 Ω cm2 upon annealing at 530 °C in air. X-ray photoemission spectroscopy (XPS) Ga 3d core levels obtained from the interface regions before and after annealing indicate a large band bending of p-GaN (about 1.7-1.8 eV), namely, an increase of Schottky barrier height. Based on the XPS, secondary ion mass spectroscopy, and capacitance-voltage data, possible transport mechanisms for the annealed contacts are described and discussed.