Leakage Reduction of Quasi-Vertical GaN Schottky Barrier Diode with Post Oxygen Plasma Treatment

This work presents a quasi-vertical GaN Schottky barrier diode (SBD) on sapphire substrate with oxygen (O2) plasma treatment after mesa etching. The fabricated diodes exhibit a high ON/OFF current ratio of $10^{{10}}$ with a low OFF-state leakage current density of $10^{-{8}}$ A/cm2 at a bias voltage of-3 V and a breakdown voltage (BV) of 180 V. Transmission electron microscopy (TEM) images reveal that the O2 plasma treatment can remove the photoresist residue on the surface of GaN. As a result, the barrier height of Ni/Au anode electrode on GaN is increased and the traps caused by the addition of carbon in GaN are reduced, thus leading to a lower reverse leakage current and high BV. This work provides a good process to make GaN on foreign substrates more practical for high power electronics applications.