Importance of layer distribution in Ni and Au based ohmic contacts to p-type GaN

In this work, we report on the importance of layer distribution after annealing to form a high quality ohmic contact p-type GaN, using nickel (Ni) and gold (Au) thin association. Both standard GaN/Ni/Au its reverse, GaN/Au/Ni GaN were studied. The Au/Ni stack exhibits most promising results in study. While quasi-linear current-voltage (I-V) characteristic, counterpart, GaN/Au/Ni, shows pure behavior, with specific resistance (ρc) as low 2.0 × 10−4 Ω.cm2 rapid thermal (RTA) at 500 °C for 5 min under air ambient, equivalent best literature results. X-ray diffraction (XRD) transmission electron microscopy (TEM) analyses demonstrate incomplete inversion layers during leading GaN/Ni/Au/NiO that explains why inferior electrical performance. On other hand, annealed same conditions, excellent can be attributed both (i) presence interface allowing formation gallide solid solution (Ga-Au) (ii) NiO directly contacted p-GaN. Those two mechanisms are known lead good GaN. These although is p-GaN layers, opposite (GaN/Au/Ni) gives Ohmic behavior. This important achieving performance power diodes or transistors including p-gate structure.