Low turn-on voltage AlGaN/GaN Schottky barrier diode with a low work function anode and high work function field plate

Abstract

AlGaN/GaN Schottky barrier diodes (SBDs) with a low work function W anode and a high work function Ni field plate on sapphire substrates are investigated in this Letter. The low work function metal W leads to the low turn-on voltage, while the high work function metal Ni maintains the leakage current and increases the breakdown voltage. An ultralow turn-on voltage of 0.23 V determined by the positive fixed charge at the AlGaN/Si3N4 interface is achieved in this W/Ni SBD. More importantly, benefitting from the dual-metal anode/field plate structure, the on-resistance decreases from 7.99 to 5.53 Ω mm, and the breakdown voltage increases from 493 to 1219 V. In addition, the turn-on voltage decreases less than 57%, and the on-resistance increases less than 186% at a high temperature up to 120 °C. The W/Ni SBD with a cathode–anode length of 18 μm and a field plate length of 4 μm shows a low turn-on voltage of 0.23 V, a low on-resistance of 5.53 Ω mm, a leakage current of 0.65 mA/mm, and a high breakdown voltage of 1.21 kV, indicating a great potential for power electronic applications.