ITO/Ti/Au Ohmic contacts on n-type ZnO.

Authors :: Kang, B. S.
Chen, J. J.
Ren, F.
Li, Y.
Kim, H.-S.
Norton, D. P.
Pearton, S. J.
Source :: Applied Physics Letters; 5/1/2006, Vol. 88 Issue 18, p182101, 3p, 1 Black and White Photograph, 3 Graphs
Publication Year :: 2006
Abstract: The specific contact resistivity and chemical intermixing of indium-tin-oxide (ITO)/Ti/Au Ohmic contacts on n-type bulk ZnO substrates are reported as a function of annealing temperature up to 450 °C. A minimum contact resistivity of 4.6×10<superscript>-6</superscript> Ω cm<superscript>2</superscript> was obtained at 50 °C and the value remained <10<superscript>-5</superscript> Ω cm<superscript>2</superscript> for all temperatures up to 450 °C, suggesting that the Ti is an effective diffusion barrier which prevents formation of Au–In solid solutions. Optical microscopy of the contacts shows roughening of the morphology after annealing at 450 °C. Indium outdiffusion to the surface of the contact stack is significant by 350 °C, and Zn outdiffusion is evident by 450 °C. Both the In and underlying Ti become oxidized after these higher temperature treatments. [ABSTRACT FROM AUTHOR]