Formation of vanadium-based ohmic contacts to n-GaN

Abstract

We investigate vanadium (V)-based ohmic contacts on n-GaN (N-d=2.0x10(18) cm(-3)) as a function of annealing temperature. It is shown that the V (60 nm) contacts become ohmic with specific contact resistances of 10(-3)-10(-4) Omega cm(2) upon annealing at 650 and 850 degreesC. The V (20 nm)/Ti (60 nm)/Au (20 nm) contacts produce very low specific contact resistances of 2.2x10(-5) and 4.0x10(-6) Omega cm(2) when annealed at 650 and 850 degreesC, respectively. A comparison shows that the use of the overlayers (Ti/Au) is very effective in improving ohmic property. Based on Auger electron spectroscopy and glancing-angle x-ray diffraction results, possible explanations for the annealing temperature dependence of the ohmic behavior of the V-based contacts are described and discussed. (C) 2003 American Institute of Physics.