The improvement of low-resistance and high-transmission ohmic contact to p-GaN by Zn+ implantation

The electrical and optical characteristics of Zn+ ion-implanted Ni/Au ohmic contacts to p-GaN were investigated. After the preparation of Ni/Au electrode on the surface of p-GaN, the metal/p-GaN contact interface was doped by 35 keV Zn+ implantation with fluences of 5 × 1015–5 × 1016 cm−2. Subsequent rapid thermal annealing of the implanted samples were carried in air at 200–400 °C for 5 min. Obvious improvements of the electrode contact characteristics were observed, i.e. the decrease of specific contact resistance and the increase of light transmittance. The lowest specific contact resistance of 5.46 × 10−5 Ω cm2 was achieved by 1 × 1016 cm−2 Zn+ implantation. The transmission enhancement of the electrodes was found as the annealing temperature rises. Together with the morphology and structure analyses of the contacts by scanning and transmission electron microscope, the corresponding mechanism for such an improvement was discussed.