Investigation of Ni/Au-contacts on p-GaN annealed in different atmospheres

We investigated the effect of different annealing atmospheres on contact be haviour of Ni/Au contacts on moderately doped p-GaN layers. We used the ann ealing gases N-2, O-2, Ar, and forming gas (N-2/H-2) at varying annealing t emperatures from 350 degreesC to 650 degreesC in steps of 50 degreesC. The p-GaN samples were either metalorganic chemical vapor deposition or molecul ar beam epitaxy grown. Contact characterization was done after each anneali ng step by using the circular transmission line model. Specific contact res istances were determined to be in the low 10 (4)Omega cm(2) range for oxidi zed contacts. Accompanying chemical analysis using depth resolved Auger ele ctron spectroscopy revealed that NiO was formed and Au diffused towards the interface, whereas annealing in forming gas prevented oxidation and did no t lead to Ohmic behaviour. (C) 2001 Elsevier Science B.V. All rights reserv ed.