NiO removal of Ni/Au Ohmic contact to p-GaN after annealing

Abstract

The Ni/Au contact was treated with oxalic acid after annealing in O2 ambient, and its I–V characteristic showed the property of contact has been obviously improved. An Auger electron spectroscopy (AES) depth profile of the contact as-annealed showed that the top layer was highly resistive NiO, while an X-ray photo-electron spectroscopy (XPS) of oxalic acid treated samples indicated that the NiO has been removed effectively. A scanning electron microscope (SEM) was used to observe the surface morphology of the contacts, and it was found that the lacunaris surface right after annealing became quite smooth with lots of small Au exposed areas after oxalic acid treatment. When the test probe or the subsequently deposited Ti/Au was directly in contact with these small Au areas, they worked as low resistive current paths and thus decrease the specific contact resistance.

High-Density μLED-Based Optical Cochlear Implant With Improved Thermomechanical Behavior

“…Following resist lift-off, the p-contacts are annealed in oxygen atmosphere at 550°C to lower the contact resistance; at this step, a Ni oxide forms at the surface. The Ni oxide is subsequently removed by oxalic acid to achieve an interface with low contact resistance ( Mengzhe et al, 2009 ) and high optical transmittance through this first layer of the p-contact. Using the same photolithography mask and AZ5214E photoresist, 100 nm of silver (Ag) is evaporated onto the preprocessed p-contact to form the reflective part of the p-contact.…”