Effects of NiO on electrical properties of NiAu-based ohmic contacts for p-type GaN

Effects of a NiO layer on the electrical properties of NiAu-based ohmic contacts for p-GaN were studied by depositing a p-type NiO layer on the p-GaN using a sputter-deposition technique. NiO layers doped with Li[NiO(Li)] had a p-type conduction with sheet resistivity of around 1 Ohm cm after annealing at temperatures lower than 500 degrees C. A variety of the NiAu-based contacts with the NiO layers such as NiO/Au, NiO(Li)/Au, Ni/NiO(Li)/Au, Ni/Li2O/NiO/Au, and Ni/Li2O/Ni/NiO/Au contacts were prepared by depositing on the p-GaN, where a slash "/" indicates the deposition sequence. However, these contacts did not provide specific contact resistances (rho(c)) lower than that (rho(c) similar to 10(-2) Ohm cm(2)) of the conventional Ni/Au contacts prepared by annealing in N-2 ambient. From the present results, it was believed that the p-NiO layer did not act as an intermediate semiconductor layer to reduce the Schottky barrier height at the p-GaN/Au interface. (C) 1999 American Institute of Physics. [S0003-6951(99)03652-9].