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 <inline-formula> <tex-math notation="LaTeX">$10^{{10}}$ </tex-math></inline-formula> with a low OFF -state leakage current density of <inline-formula> <tex-math notation="LaTeX">$10^{-{8}}$ </tex-math></inline-formula> 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.