Low-resistance and transparent ohmic contacts to p-type GaN using Zn–Ni solid solution/Au scheme

High-quality Zn–Ni solid solution(8 nm)/Au(8 nm) ohmic contacts on p-GaN (5×1017 cm−3) have been investigated by means of current–voltage (I–V) measurements and x-ray photoemission spectroscopy. The as-deposited contact shows nonlinear I–V characteristics. However, oxidizing the contacts at 530 °C for 1 min in air ambient gives rise to considerable improvement in their I–V behaviors, yielding a specific contact resistance of 5.2×10−5 Ω cm2. The light transmittance of the annealed Zn–Ni solid solution/Au contacts is measured to be better than 74% at a wavelength of 470 nm. Green light-emitting diodes (LEDs) fabricated with the annealed Zn–Ni solid solution/Au contacts give a forward-bias voltage of 3.39 V at an injection current of 20 mA, which is better than that of the LEDs with the oxidized Ni/Au contacts.