Low resistance high reflectance contacts to p-GaN using oxidized Ni/Au and Al or Ag

Abstract

We report on a high reflectance low resistance multilayer contact to p-GaN composed of a thin oxidized Ni/Au bilayer overcoated with a thick Al or Ag layer and then capped by Ni/Au. Measurements on 500 μm diameter light emitting diode-like test structures show an operating voltage below 4 V at 20 mA that is comparable to identical devices fabricated with a conventional Ni/Au contact. Back surface light emission is about 70% greater than that from devices with the Ni/Au contact due to lower light absorption by the Al or Ag. Performance for both Al and Ag based contacts is stable at temperatures of up to around 100 °C.