Modulation of barrier height in n-type GaN Schottky structure with ultrathin oxide interlayer mediated by dipole formation

The effect on the barrier height of inserting ultrathin oxide (GaOx) interlayers at n-type GaN Schottky contacts was systematically investigated. Inserting interlayers (>0.5nm) between GaN and electrode metals having relatively low electronegativities (Al, Ni, and Pd) decreased the Schottky barrier height by 0.2–0.4 eV. On the other hand, a chemically stable Au electrode exhibited almost no changes in barrier height regardless of the presence of an interlayer. X-ray photoelectron spectroscopy analyses revealed that a dipole formed through a redox reaction at the low-electronegativity metal/GaOx interfaces, causing an abrupt energy-band shift and significant change in the Schottky barrier height.